Which Dichlor To Use?

[TinyBubbles]

I have an ozonator, circulation pump, N2, dose with dichlor after soaking and shock weekly with mps. I've been using the dichlor that came in my start up kit and it shows 99% dichlor. I just went to the supply store and they said to use 55% dichlor, because the whole point of using N2 is to cut down your chemical usage. I asked why I couldn't continue to use the 99% dichlor and just use less of it. They said not to, but didn't give any real science behind it. Does this make sense to any of you?

[Jetman]

I have an ozonator, circulation pump, N2, dose with dichlor after soaking and shock weekly with mps. I've been using the dichlor that came in my start up kit and it shows 99% dichlor. I just went to the supply store and they said to use 55% dichlor, because the whole point of using N2 is to cut down your chemical usage. I asked why I couldn't continue to use the 99% dichlor and just use less of it. They said not to, but didn't give any real science behind it. Does this make sense to any of you?

HEY TINY!!

I can't answer that question, but it sounds like a question for CHEM GEEK!! LOL He really knows his water chemistry!! I took his advice and switched over to 4oz of bleach once per day and my water has been great! My CYA levels were getting kinda high with the dichlor, which would eventually make the dichlo less effective, as he explained in a previous post. Not to mention the bleach will be MUCH CHEAPER!!! I also use the N2 and MPS shock once or twice per week depending on usage. The Dichlor I was using was 99% by SpaGuard. I didn't know there was another option!

Our weather has turned to FALL temps finally!!! 60 days/ 40eve. Starting to really enjoy those soaks even more!!! BTW... are you being affected by the fires??? How far away are you??

Let me know how you make out!

Paul

[biggz]

TinyBubbles, I also use 99% Dichlor from "Aqua Chem" which is basically vinyl pool shock. I use it to super chlorinate my fiberglass pool, but in the hot tub I add 1 oz once a week and use 1 oz of liquid chlorine every 2 days regardless my use. I also use N2 and the enzymes that came with the kit. The water quality is excellent. I've been thinking of changing to bleach as well but I'm more familiar with the liquid chlorine.

[TinyBubbles]

Ok, I got a chance at lunch to read the bottle. It's 55% chlorine because the rest of it is clarifiers, buffers, etc. That is not what I want. I'm kinda in a pickle, cause it's a friend of mine in the "business" and it's hard to tell them that you don't want to follow their advice. It's even worse, because they are selling me everything at cost. I'm dreading going back over there, but I guess I have to. On the bleach issue, I don't think I'll switch over. I think it would be a matter of time before I splashed or spilled it on something. I'm assuming the cost in ruined clothes would outweigh any money saved.

Luckily, I am nowhere near the fires. I am actually on the east coast.

[tony]

Ok, I got a chance at lunch to read the bottle. It's 55% chlorine because the rest of it is clarifiers, buffers, etc. That is not what I want. I'm kinda in a pickle, cause it's a friend of mine in the "business" and it's hard to tell them that you don't want to follow their advice. It's even worse, because they are selling me everything at cost. I'm dreading going back over there, but I guess I have to. On the bleach issue, I don't think I'll switch over. I think it would be a matter of time before I splashed or spilled it on something. I'm assuming the cost in ruined clothes would outweigh any money saved.

Luckily, I am nowhere near the fires. I am actually on the east coast.

Most of the rest of dichlor is CYA and not buffers or clarifiers. All chlorines, except chlorine gas, contain other products from the manufacturing process to make them usable. Bleach at 5% available chlorine is almost 95% water with a bit of salt. I agree...bleach is difficult to handle and probably is the reason why it is not preferred by manufacturers and why I do not use it regularly.

[chem geek]

I'm sure this is more than you want to know, but if you're interested you can read it; otherwise skip it.

Dichlor is almost always sold in near pure form, so 99% sounds about right. The 55% number refers to what is known as "Available Chlorine" which is the weight percent of chlorine in the product relative to the weight of chlorine gas that would produce the same amount of Free Chlorine in water. Technically, this form of Dichlor is "dihydrate" meaning it also has two water molecules with every Dichlor molecule. The anhydrous (water-free) form of Dichlor is 65% Available Chlorine, but is somewhat more hazardous (for transportation and storage) so is not what is typically sold. As was stated in the previous post, the other component of Dichlor is Cyanuric Acid (CYA). Technically, Dichlor is 49% Cyanuric Acid (technically, cyanurate ion), 14% water and 9% Sodium by weight. That leaves 28% by weight for the chlorine and the reason that the Available Chlorine is 55% is that only one of the two chlorine atoms in chlorine gas becomes disinfecting chlorine (hypochlorous acid) whereas each of the two chlorine atoms in Dichlor become disinfecting chlorine so it takes twice as much chlorine gas by weight to have the same effect (and roughly 55% is double 28% if we ignore rounding error in my calculations).

You can't really go by the Available Chlorine number to figure out what else is in the product. Trichlor, for example, is 92% Available Chlorine, yet contains 54% CYA (actually, cyanurate ion) by weight. That leaves 46% for chlorine and note that doubling this gives you 92% as explained above. The Available Chlorine does tell you essentially how "dense" or efficient the product is in terms of the amount of weight that is a chlorine gas equivalent, but that's far less important than knowing the other details about the products side effects such as increasing CYA levels or decreasing pH, etc.

Richard

[biggz]

I'm sure this is more than you want to know, but if you're interested you can read it; otherwise skip it.

Dichlor is almost always sold in near pure form, so 99% sounds about right. The 55% number refers to what is known as "Available Chlorine" which is the weight percent of chlorine in the product relative to the weight of chlorine gas that would produce the same amount of Free Chlorine in water. Technically, this form of Dichlor is "dihydrate" meaning it also has two water molecules with every Dichlor molecule. The anhydrous (water-free) form of Dichlor is 65% Available Chlorine, but is somewhat more hazardous (for transportation and storage) so is not what is typically sold. As was stated in the previous post, the other component of Dichlor is Cyanuric Acid (CYA). Technically, Dichlor is 49% Cyanuric Acid (technically, cyanurate ion), 14% water and 9% Sodium by weight. That leaves 28% by weight for the chlorine and the reason that the Available Chlorine is 55% is that only one of the two chlorine atoms in chlorine gas becomes disinfecting chlorine (hypochlorous acid) whereas each of the two chlorine atoms in Dichlor become disinfecting chlorine so it takes twice as much chlorine gas by weight to have the same effect (and roughly 55% is double 28% if we ignore rounding error in my calculations).

You can't really go by the Available Chlorine number to figure out what else is in the product. Trichlor, for example, is 92% Available Chlorine, yet contains 54% CYA (actually, cyanurate ion) by weight. That leaves 46% for chlorine and note that doubling this gives you 92% as explained above. The Available Chlorine does tell you essentially how "dense" or efficient the product is in terms of the amount of weight that is a chlorine gas equivalent, but that's far less important than knowing the other details about the products side effects such as increasing CYA levels or decreasing pH, etc.

Richard

'chem geek' Richard can liquid chlorine be used instead of bleach as a chlorine alternative?

[tony]

'chem geek' Richard can liquid chlorine be used instead of bleach as a chlorine alternative?

Obviously I am not Richard, but...liquid chlorine generally sold at pool stores as a pool shock is the same as bleach except it is double strength. Where household bleach is 5-6% available chlorine, liquid chlorine is 10-12%. I find it to be a good value. Liquid chlorine sells in my area about $4.00 per gallon. That equivalent to $2 bleach.

[jmo]

This is a great thread and Tiny Bubbles, you lead the way in practical questions. Also I liked your spa pictures!

Thanks everyone here for teaching us newbies about how to keep our water perky.

Chemgeek: it there a quick check list you might compose for us incorporating the bleach with the others?

I get my Spa Monday, and if it's a nice day, may take some pictures of it too. That would help force me to learn Photobucket's use, which is so clearly outlined in another thread.

This site is truly a wonderful aide. Thank you all.

jmo

[biggz]

'chem geek' Richard can liquid chlorine be used instead of bleach as a chlorine alternative?

Obviously I am not Richard, but...liquid chlorine generally sold at pool stores as a pool shock is the same as bleach except it is double strength. Where household bleach is 5-6% available chlorine, liquid chlorine is 10-12%. I find it to be a good value. Liquid chlorine sells in my area about $4.00 per gallon. That equivalent to $2 bleach.

'tony', I know you know your chems too, so should I use less liquid chlorine? I'm using 1 oz now. Could I cut it back to say 1/2 an oz and get the same results while I'm still using the N2 and enymes? I must admit that 1 oz seems to be working fine, but less usable chlorine is a good thing.

[TinyBubbles]

We would love to see your pics JMO. The product I was referring to that is 55% chlorine was spa essentials spa shock xtra. I checked the label and it said 58% chlorine and 41% other ingredients. On the back of the bottle it said it was a mix of chlorine and clarifiers and buffers. It, also, said it was not to be used as a sanitizer, only a shock. In my opinion, if I wanted to add buffers and clarifiers, I would do it. I don't see any point in having them mixed in with my chlorine. Plus, I wanted the chlorine as a sanitizer, not a shock. I returned it and bought the straight chlorine sanitizer that is 99% chlorine on the label. I'm assuming this is around 55 to 56% free chlorine, just like the spa 56 I originally used. Thanks to forums like this, I think many of us are more informed than the people working at the stores selling the chemicals.

[tony]

'tony', I know you know your chems too, so should I use less liquid chlorine? I'm using 1 oz now. Could I cut it back to say 1/2 an oz and get the same results while I'm still using the N2 and enymes? I must admit that 1 oz seems to be working fine, but less usable chlorine is a good thing.

Most of what I know is what I have experienced. Richard KNOWS his chems.

biggz, what enzymes are you using? Certain enzyme systems will allow you to use very little chlorine while other enzyme additives help with oils and scum but not bacteria.

[chem geek]

I checked the label and it said 58% chlorine and 41% other ingredients.

So I was wrong about that particular product. If it has an ingredients list that says 58% for "Sodium Dichloro-s-Triazine-Trione Dihydrate" or something that sounds similar to that, then that is indeed a diluted product and would have only 32% Available Chlorine (55% * 0.58). As you said, it is good to check the ingredients. You can also look up a Material Safety Data Sheet (MSDS) for the product online or ask for it at the store (if they have it) as that will also list the ingredients (though for some chemicals they are just shown as "proprietary").

[chem geek]

'chem geek' Richard can liquid chlorine be used instead of bleach as a chlorine alternative?

Tony answered your question (the answer is "Yes"). You do need to be careful and check the concentration on the bottle since chlorinating liquid comes in different concentrations -- usually 12.5% or 10%. The higher concentrations degrade faster (in the bottle when concentrated; not in your pool or spa) and it goes roughly as the square of the concentration so that means that 12.5% chlorinating liquid degrades about 4 times faster than 6%. The table at the bottom of this link shows the half-life of chlorine vs. concentration and temperature. This half-life is the time it takes for the chlorine to lose half of its strength. There is a more rapid loss of strength initially and it slows down as the concentration drops. It is important to keep the chlorine away from heat and sunlight or it will degrade rapidly.

I have checked the concentration from my local pool store and find they are very good at maintaining their chlorine -- they have high turnover and store the chlorine out of sunlight. You can test the chlorine via dilution by doing two 1:100 dilutions (1 ounce in 6-1/4 cups of filtered or distilled water then repeat) but that is hard to do accurately unless you have a calibrated measuring pipette or tube. If you know your pool water volume, then you can just see if the Free Chlorine (FC) went up as much as expected. The concentration should match the ppm FC rise when 1 gallon is added to 10,000 gallons so one gallon of 12.5% chlorinating liquid in 10,000 gallons of pool water should raise the FC by 12.5 ppm.

There are some subtleties to keep in mind when comparing pricing for bleach vs. chlorinating liquid. The most important is to realize that most bleach is sold in 96 ounce (3/4 gallon) containers, not gallon containers, while chlorinating liquid is usually sold by the gallon. Sometimes, bleach is sold in larger 1.5 gallon containers. Another point is that only Clorox Regular unscented bleach is registered with the EPA so has to show the concentration in the ingredients which is 6% Sodium hypochlorite and also shows the Available Chlorine of 5.7%. Other brands of bleach are usually weaker, but "Ultra" is often 6% while off-brand Regular is sometimes 3% or even lower.

There is also a subtlety to how chlorine concentration is measured which differs between bleach and chlorinating liquid. The ingredients list on Clorox Regular bleach that says 6% is referring to the weight percentage of Sodium hypochlorite. Most chlorine measurements, including Available Chlorine, Free Chlorine, etc. are based on the weight of the equivalent amount of Chlorine Gas that would result in the same amount of chlorine in water (and remember that only half of the chlorine in the gas results in chlorine in water -- the other half results in chloride ion). Available Chlorine therefore differs from the ingredients percentage by the ratio of molecular weights of Sodium hypochlorite (74.4422 g/mole) vs. chlorine gas (70.906 g/mole) so 6% * 70.906 / 74.4422 = 5.715%. To make things even more confusing, chlorinating liquid is usually specified in what is known as "Trade %" which is the Volume % that is equivalent to chlorine gas in terms of its chlorine content in water. It is essentially the Volume % of Available Chlorine. So the Trade % is the Weight % Available Chlorine multiplied by the density of the liquid (in g/ml). The good news about Trade % is that it allows for an easy calculation since 12.5% Trade of chlorinating liquid has one gallon in 10,000 gallons increase Free Chlorine by 12.5 ppm exactly. So, 12.5% Trade is 12.5/1.14 = 10.96% Available Chlorine and is 10.96% * 74.4422 / 70.906 = 11.51% Sodium hypochlorite. Some chlorinating liquid bottles show an ingredients list similar to bleach, but in fact the percentage listed is a Trade % but since all of these are somewhat close and the chlorine degrades, this is all just subtlety. The bottom line is that 6% bleach is 52% of the strength of 12.5% chlorinating liquid so using a "half" for comparison of equivalent volumes for pricing is quite reasonable.

As an example, I can get 12.5% chlorinating liquid from my pool store for $3.50 (includes tax) per gallon and that is roughly equivalent to $3.50 * 96 / 128 / 2 = $1.31 for a 96 ounce jug of 6% bleach.

Richard

[chem geek]

Chemgeek: it there a quick check list you might compose for us incorporating the bleach with the others?

I'm not sure what you are looking for. Are you asking for equivalent amounts of product that produce the same amount of chlorine in water? To raise the Free Chlorine (FC) by 1 ppm in 500 gallons of water (so multiply by your water volume and divide by 500), takes 1.0 fluid ounces of 6% bleach or 0.12 ounces weight (which is about 0.12 fluid ounces or 0.72 teaspoons). So adding just 1 fluid ounce of bleach to a spa is very little chlorine and probably far less than the amount of chlorine in Dichlor that you usually add. If you have a 350 gallon spa, then you probably use around 4 ppm FC per day and need to add that much each day if its used every day. To raise the FC by 4 ppm in 350 gallons it would take 2.9 (about 3) fluid ounces of 6% bleach or 0.34 ounces weight (about 0.34 fluid ounces or 2.0 teaspoons) of Dichlor.

So the general rule is that 3 fluid ounces of 6% bleach is equivalent to 2 teaspoons of Dichlor in terms of chlorine content, but of course the Dichlor also increases the Cyanuric Acid (CYA) level. So don't skimp on the bleach -- it's not nearly as concentrated in chlorine by weight or volume as Dichlor. Bleach is mostly water.

Richard

[biggz]

'tony', I know you know your chems too, so should I use less liquid chlorine? I'm using 1 oz now. Could I cut it back to say 1/2 an oz and get the same results while I'm still using the N2 and enymes? I must admit that 1 oz seems to be working fine, but less usable chlorine is a good thing.

Most of what I know is what I have experienced. Richard KNOWS his chems.

biggz, what enzymes are you using? Certain enzyme systems will allow you to use very little chlorine while other enzyme additives help with oils and scum but not bacteria.

'tony', I'm using the enzymes product from the "Leisure Time" start up kit. It's suppose to break down scum and help eliminate water lines. So far it's been pretty good. I'll probably change to Spa Perfect from " Natural Chemistry" once this bottle is finished though. I use their pool product with excellent results. I don't have to use as much chlorine because they make a product call "Pool Perfect/Phosfree" which eliminates the phosphates in the pool starving the algae. It also makes the water feel silky to the skin.

[biggz]

'chem geek' Richard can liquid chlorine be used instead of bleach as a chlorine alternative?

Tony answered your question (the answer is "Yes"). You do need to be careful and check the concentration on the bottle since chlorinating liquid comes in different concentrations -- usually 12.5% or 10%. The higher concentrations degrade faster (in the bottle when concentrated; not in your pool or spa) and it goes roughly as the square of the concentration so that means that 12.5% chlorinating liquid degrades about 4 times faster than 6%. The table at the bottom of this link shows the half-life of chlorine vs. concentration and temperature. This half-life is the time it takes for the chlorine to lose half of its strength. There is a more rapid loss of strength initially and it slows down as the concentration drops. It is important to keep the chlorine away from heat and sunlight or it will degrade rapidly.

I have checked the concentration from my local pool store and find they are very good at maintaining their chlorine -- they have high turnover and store the chlorine out of sunlight. You can test the chlorine via dilution by doing two 1:100 dilutions (1 ounce in 6-1/4 cups of filtered or distilled water then repeat) but that is hard to do accurately unless you have a calibrated measuring pipette or tube. If you know your pool water volume, then you can just see if the Free Chlorine (FC) went up as much as expected. The concentration should match the ppm FC rise when 1 gallon is added to 10,000 gallons so one gallon of 12.5% chlorinating liquid in 10,000 gallons of pool water should raise the FC by 12.5 ppm.

There are some subtleties to keep in mind when comparing pricing for bleach vs. chlorinating liquid. The most important is to realize that most bleach is sold in 96 ounce (3/4 gallon) containers, not gallon containers, while chlorinating liquid is usually sold by the gallon. Sometimes, bleach is sold in larger 1.5 gallon containers. Another point is that only Clorox Regular unscented bleach is registered with the EPA so has to show the concentration in the ingredients which is 6% Sodium hypochlorite and also shows the Available Chlorine of 5.7%. Other brands of bleach are usually weaker, but "Ultra" is often 6% while off-brand Regular is sometimes 3% or even lower.

There is also a subtlety to how chlorine concentration is measured which differs between bleach and chlorinating liquid. The ingredients list on Clorox Regular bleach that says 6% is referring to the weight percentage of Sodium hypochlorite. Most chlorine measurements, including Available Chlorine, Free Chlorine, etc. are based on the weight of the equivalent amount of Chlorine Gas that would result in the same amount of chlorine in water (and remember that only half of the chlorine in the gas results in chlorine in water -- the other half results in chloride ion). Available Chlorine therefore differs from the ingredients percentage by the ratio of molecular weights of Sodium hypochlorite (74.4422 g/mole) vs. chlorine gas (70.906 g/mole) so 6% * 70.906 / 74.4422 = 5.715%. To make things even more confusing, chlorinating liquid is usually specified in what is known as "Trade %" which is the Volume % that is equivalent to chlorine gas in terms of its chlorine content in water. It is essentially the Volume % of Available Chlorine. So the Trade % is the Weight % Available Chlorine multiplied by the density of the liquid (in g/ml). The good news about Trade % is that it allows for an easy calculation since 12.5% Trade of chlorinating liquid has one gallon in 10,000 gallons increase Free Chlorine by 12.5 ppm exactly. So, 12.5% Trade is 12.5/1.14 = 10.96% Available Chlorine and is 10.96% * 74.4422 / 70.906 = 11.51% Sodium hypochlorite. Some chlorinating liquid bottles show an ingredients list similar to bleach, but in fact the percentage listed is a Trade % but since all of these are somewhat close and the chlorine degrades, this is all just subtlety. The bottom line is that 6% bleach is 52% of the strength of 12.5% chlorinating liquid so using a "half" for comparison of equivalent volumes for pricing is quite reasonable.

As an example, I can get 12.5% chlorinating liquid from my pool store for $3.50 (includes tax) per gallon and that is roughly equivalent to $3.50 * 96 / 128 / 2 = $1.31 for a 96 ounce jug.

Richard

Richard, So in addition to using the N2 and the enzyme additive is this the reason that I can go 2-3 days per application and still maintain clear water. I'm trying to obtain an almost chlorineless tub environment.

[tony]

'tony', I'm using the enzymes product from the "Leisure Time" start up kit. It's suppose to break down scum and help eliminate water lines. So far it's been pretty good. I'll probably change to Spa Perfect from " Natural Chemistry" once this bottle is finished though. I use their pool product with excellent results. I don't have to use as much chlorine because they make a product call "Pool Perfect/Phosfree" which eliminates the phosphates in the pool starving the algae. It also makes the water feel silky to the skin.

I like the enzyme products you're using. I use the LT Enzyme myself during heavy use season. Gives the water a fresh feel. These enzymes don't reduce bacteria, though, such as Eco One or the Natural. Your Nature2 does though and helps maintain water especially when there are times of non use. Don't skimp on the chlorine though if you add after soaking. It goes away by itself quick enough.

[chem geek]

Richard, So in addition to using the N2 and the enzyme additive is this the reason that I can go 2-3 days per application and still maintain clear water. I'm trying to obtain an almost chlorineless tub environment.

Clear water is relatively easy. You just need either enzymes (plus an oxidizer such as chlorine) or shock (non-chlorine or chlorine). The harder part is not having the chlorine go away to zero quickly. Use of non-chlorine shock helps that since its an oxidizer so can get rid of organics before chlorine does. Enzymes do not do that, but rather speed up the breakdown of organics and the chlorine will still get used up rather quickly (there is a little savings in chlorine from using enzymes because dissolved oxygen is also an oxidizer though much weaker than chlorine so the enzymes let this oxygen break down some organics in place of having the chlorine do so). Enzymes are catalysts so speed up reactions -- they are not oxidizers by themselves (you can think of them as assisting the chlorine in breaking down the organics, but the chlorine still gets used up). The N2 doesn't do that much except help the chlorine kill pathogens faster, but won't cut down chlorine usage (at least in a spa -- in a pool exposed to sunlight, the copper in N2 can help prevent algae and that helps reduce chlorine usage a little bit -- more chlorine is consumed preventing algae growth than bacterial growth, though the most is consumed by organics and by breakdown from sunlight).

Remember that the purpose of the chlorine is as a fast-acting disinfectant. It prevents bacteria and viruses going the fecal-to-oral route and that requires relatively fast killing. The N2 (silver) won't do that nor will the enzymes nor non-chlorine shock (MPS). By the way, clear water means nothing in terms of sanitation. Teaming bacteria, protozoa and viruses do not usually show up visibly in water.

Also remember that with Cyanuric Acid (CYA) in the water, the actual disinfecting chlorine concentration is VERY low. It's this disinfecting chlorine that you smell as a clean bleach smell (if you smell something smellier, then that's chloramines which is chlorine combined with ammonia), that wears on your skin and hair and swimsuits, etc. Assuming that the silver in the N2 combined with chlorine helps kill the hot tub itch bacteria faster, then you could have a higher CYA level in the water for a lower disinfecting chlorine level. But if you try to just lower the Free Chlorine (FC) level down to 1 ppm or less, you will very likely have it used up very quickly and go to zero. That's the problem that is to be avoided and N2 won't help that at all and enzymes only help it a little. Non-chlorine shock (MPS) probably helps the most, but you will still lose chlorine through outgassing from the hot water and aeration from jets though this loss slows down as the concentration drops.

When you say you can go 2-3 days without adding chlorine, are you saying that you still have a measurable chlorine level after 3 days? If so, do you use the tub every day? Such a small loss would be unusual unless your temps are lower or don't aerate as much or have a larger tub or are very clean and don't sweat

Why do you want to minimize the chlorine level? What problem are you trying to solve by doing that? Health hazards come from chloramines and chlorine combined with some organics (e.g. trihalomethane), not from chlorine (hypochlorous acid) itself. So if that is your primary concern, using a non-chlorine shock (MPS) is the best way to get rid of the ammonia and organics before chlorine combines with them. The enzymes and the N2 won't do that.

Richard

[biggz]

Richard, So in addition to using the N2 and the enzyme additive is this the reason that I can go 2-3 days per application and still maintain clear water. I'm trying to obtain an almost chlorineless tub environment.

Clear water is relatively easy. You just need either enzymes (plus an oxidizer such as chlorine) or shock (non-chlorine or chlorine). The harder part is not having the chlorine go away to zero quickly. Use of non-chlorine shock helps that since its an oxidizer so can get rid of organics before chlorine does. Enzymes do not do that, but rather speed up the breakdown of organics and the chlorine will still get used up rather quickly (there is a little savings in chlorine from using enzymes because dissolved oxygen is also an oxidizer though much weaker than chlorine so the enzymes let this oxygen break down some organics in place of having the chlorine do so). Enzymes are catalysts so speed up reactions -- they are not oxidizers by themselves (you can think of them as assisting the chlorine in breaking down the organics, but the chlorine still gets used up). The N2 doesn't do that much except help the chlorine kill pathogens faster, but won't cut down chlorine usage (at least in a spa -- in a pool exposed to sunlight, the copper in N2 can help prevent algae and that helps reduce chlorine usage a little bit -- more chlorine is consumed preventing algae growth than bacterial growth, though the most is consumed by organics and by breakdown from sunlight).

Remember that the purpose of the chlorine is as a fast-acting disinfectant. It prevents bacteria and viruses going the fecal-to-oral route and that requires relatively fast killing. The N2 (silver) won't do that nor will the enzymes nor non-chlorine shock (MPS). By the way, clear water means nothing in terms of sanitation. Teaming bacteria, protozoa and viruses do not usually show up visibly in water.

Also remember that with Cyanuric Acid (CYA) in the water, the actual disinfecting chlorine concentration is VERY low. It's this disinfecting chlorine that you smell as a clean bleach smell (if you smell something smellier, then that's chloramines which is chlorine combined with ammonia), that wears on your skin and hair and swimsuits, etc. Assuming that the silver in the N2 combined with chlorine helps kill the hot tub itch bacteria faster, then you could have a higher CYA level in the water for a lower disinfecting chlorine level. But if you try to just lower the Free Chlorine (FC) level down to 1 ppm or less, you will very likely have it used up very quickly and go to zero. That's the problem that is to be avoided and N2 won't help that at all and enzymes only help it a little. Non-chlorine shock (MPS) probably helps the most, but you will still lose chlorine through outgassing from the hot water and aeration from jets though this loss slows down as the concentration drops.

When you say you can go 2-3 days without adding chlorine, are you saying that you still have a measurable chlorine level after 3 days? If so, do you use the tub every day? Such a small loss would be unusual unless your temps are lower or don't aerate as much or have a larger tub or are very clean and don't sweat

Why do you want to minimize the chlorine level? What problem are you trying to solve by doing that? Health hazards come from chloramines and chlorine combined with some organics (e.g. trihalomethane), not from chlorine (hypochlorous acid) itself. So if that is your primary concern, using a non-chlorine shock (MPS) is the best way to get rid of the ammonia and organics before chlorine combines with them. The enzymes and the N2 won't do that.

Richard

Richard, That's a lesson learned. I exaggerated and should have said 2 days since I haven't gone 3 days except when I went away resently. When I returned there was no measurable chlorine level. I also have any ozonator installed on the tub that I forgot to mention. When I add liquid chlorine I get a 1 ppm FC reading after 4 hours. We generally have been soaking for 20 mins @ 101 * at night. The next day when I check the water mid day, I'll still show .5 chlorine or some readable residual. If I soak that night I won't add any addition liquid chlorine until the next day usually in the afternoon.

But I'm getting the impression that I should be using more chlorine. I can tolerate the smell of chlorine but less smell when possible is a good thing.

[Shaamus]

Being a spa cover manufacturer, I thought I would add a bit to your discussion about which dichlor to use. In almost all cases, if you use a chlorine/sanitizer product that is not specifically formulated for use in spas, you will void your cover's warranty. Other component manufacturers may take similiar stances. Be very careful when you choose your chlorine. I am not aware of any liquid chlorine product that is formulated for spas with the possible exception of Sanygen.

I must admit that I am a bit confused by people referring to a 99% spa chlorine product. Tiny - what was the brand and name of the 99% straight sanitizer product? Was it formulated for spas?

[chem geek]

Richard, That's a lesson learned. I exaggerated and should have said 2 days since I haven't gone 3 days except when I went away resently. When I returned there was no measurable chlorine level. I also have any ozonator installed on the tub that I forgot to mention. When I add liquid chlorine I get a 1 ppm FC reading after 4 hours. We generally have been soaking for 20 mins @ 101 * at night. The next day when I check the water mid day, I'll still show .5 chlorine or some readable residual. If I soak that night I won't add any addition liquid chlorine until the next day usually in the afternoon.

But I'm getting the impression that I should be using more chlorine. I can tolerate the smell of chlorine but less smell when possible is a good thing.

OK, that makes more sense. The ozonator should help break down organics, though it won't do so as quickly as non-chlorine shock since the water has to get circulated through the ozonator, but that's not a big deal. It just means that you might smell some monochloramine which forms very quickly and that hadn't yet passed through the ozonator. If you had a residual of non-chlorine shock (MPS) instead, then you might not get as much monochloramine formation. Monochloramine is what most people smell as the "bad smell" of chlorine -- it's not like the "clean" smell of chlorine bleach. It's chlorine combined with ammonia. There are other chloramines that can form (dichloramine and nitrogen trichloride) and these smell even worse, but these are minimally formed at normal pH and with low chlorine levels (FC/CYA ratio), but with your ozonator and fast circulation, these latter chloramines are probably not getting created to any significant extent as they form more slowly.

If you use a higher chlorine level and want to reduce the smell, just be sure to uncover the spa for at least 10 minutes to air it out before you get in. Most of the issues with smell have to do with the chlorine that builds up under the cover. Also, remember the FC/CYA ratio. The true amount of disinfecting chlorine (hypochlorous acid) which is the only one that disinfects, oxidizes, and smells like chlorine bleach is proportional to the FC/CYA ratio. So keeping the chlorine low doesn't have to be done only by keeping the FC low. You can also accomplish the same thing by having the CYA higher. For whatever amount of Dichlor you add that increases the FC by 1.0 ppm, it will also increase CYA by 0.9 ppm.

My very conservative recommendation to avoid hot tub itch is an FC/CYA ratio of 0.2 (e.g. 4 ppm FC with 20 ppm CYA), but as I've said before, that may be overly conservative. Your ozonator should help kill the hot tub itch bacteria as long as its not stuck in a biofilm on a spa surface.

Richard

[chem geek]

Being a spa cover manufacturer, I thought I would add a bit to your discussion about which dichlor to use. In almost all cases, if you use a chlorine/sanitizer product that is not specifically formulated for use in spas, you will void your cover's warranty. Other component manufacturers may take similiar stances. Be very careful when you choose your chlorine. I am not aware of any liquid chlorine product that is formulated for spas with the possible exception of Sanygen.

I must admit that I am a bit confused by people referring to a 99% spa chlorine product. Tiny - what was the brand and name of the 99% straight sanitizer product? Was it formulated for spas?

The 99% refers to the Dichlor content, not the chlorine content. If you look on the ingredients label, it may say something like

INGREDIENTS:

Sodium Dichloro-s-Triazine-Trione Dihydrate 99%

But the above is just 55% Available Chlorine.

The part about chlorine/sanitizer products not specifically formulated for use in spas is just pure bunk from chemical manufacturers and/or distributors and stores that want to sell highly marked up sources of chlorine. When ALL forms of chlorine dissolve or get mixed with water, they ALL form exactly the same chlorine compounds of hypochlorous acid and hypochlorite ion (and chlorinated cyanurates if Cyanuric Acid is present). The only differences are what ELSE is added by the chlorine and in the case of most Dichlor products (the relatively "pure" ones such as described above), the only other thing they add to the water is Cyanuric Acid (CYA). Read this link on why exclusive Dichlor use can be a problem in hot tubs and spas. I believe their recommendation to not use it at all is too extreme. Some CYA is good as it prevents from having too high a disinfecting chlorine level.

The following is a description of all sources of chlorine (except chlorine gas) and their side effects. Any can be used in a spa or hot tub so long as one understands their effects from the extras that they add or what they do to water chemistry, though from a practical point of view only Dichlor and Sodium Hypochlorite (unscented bleach) make the most sense to use. Notice that all of these produce Hypochlorous Acid which is chlorine in water.

Trichlor. Normally sold as a puck or pellet. This is the most concentrated source of chlorine (by weight or volume) and is 92% Available Chlorine. The pucks or pellets are slow-dissolving and usually put into a floating feeder. This source of chlorine is VERY acidic so usually requires a base to be added periodically to maintain pH, such as Sodium Carbonate (pH Up or Arm & Hammer Super Washing Soda) or 20 Mule Team Borax. I would not recommend this for a spa or hot tub because of its strong effect on pH and you'd want to be careful that the feeder didn't park itself near an edge with the circulation off since the acidity can be destructive to surfaces. If the circulation was always on, then the risk is lower. Trichlor is chlorine plus Cyanuric Acid (CYA). For every 1.0 ppm Free Chlorine (FC) added by Trichor, it also increases CYA by 0.6 ppm.

Trichlor + Water --> Cyanuric Acid (CYA) + Hypochlorous Acid

Dichlor. This is a fast-dissolving powder or granules. It is a reasonably concentrated source of chlorine and the most common form (dihydrate) is 55% Available Chlorine. Technically, Dichlor is also acidic when accounting for chlorine usage as well as addition. Dichlor upon addition is only very slightly acidic, but the usage of chlorine is more acidic. In a spa or hot tub where there is lots of aeration due to the jets, having a somewhat net acidic chlorine source/usage such as Dichlor is reasonable as one can just maintain a higher TA level as needed. Over time, one may need to add Sodium Bicarbonate (Alkalinity Up or Arm & Hammer Baking Soda) or possibly a base as listed under Trichlor above. Dichlor is chlorine plus Cyanuric Acid (CYA). For every 1.0 ppm FC added by Dichlor, it also increases CYA by 0.9 ppm.

Dichlor + Water --> Cyanuric Acid (CYA) + Hypochlorous Acid + Sodium Hydroxide (sodium ion plus hydroxide ion)

Cal-Hypo. This is usually in slower dissolving granules and must generally be pre-mixed in a bucket of water before addition so that it does not settle to the bottom. This is a hypochlorite source of chlorine and like all such hypochlorite sources, the initial addition of chlorine is basic/alkaline and makes the pH rise, but the usage of chlorine is acidic and makes the pH drop so the net result is pH neutral. For chlorine that outgasses (such as when the jets run), then the net effect is a rise in pH. The main way to compensate for this is to lower the Total Alkalinity (TA) since that reduces the pH rise from the outgassing of carbon dioxide which is the primary source of pH rise in a spa or hot tub. Cal-Hypo is chlorine plus calcium. For every 1.0 ppm FC added by Cal-hypo, it also increases Calcium Hardness by 0.7 ppm.

Cal-Hypo + Water --> Hypochlorous Acid + Calcium Hydroxide (calcium ion plus hydroxide ion) + Salt (sodium ion plus chloride ion)

Lithium Hypochlorite. This is a fast-dissolving powder. It is the most expensive source of chlorine. It is a hypochlorite source of chlorine so the discussion above with Cal-Hypo applies, but it does not add Calcium. The lithium that is added is essentially inert.

Lithium Hypochlorite + Water --> Hypochlorous Acid + Lithium Hydroxide (lithium ion plus hydroxide ion) + Salt (sodium ion plus chloride ion)

Sodium Hypochlorite. This is bleach or chlorinating liquid. It is the most diluted source of chlorine. It is a hypochlorite source of chlorine so the discussion above with Cal-Hypo applies, but it does not add Calcium. The sodium that is added is essentially inert. The bleach or chlorinating liquid is denser than water so it is important to pour it very slowly over a return flow in the main body of water with the pump running so as to thoroughly circulate the chlorine so that it does not settle to the bottom. Once mixed, however, it stays mixed. If using bleach, it must be unscented so that it does not have any additives in it. Clorox Regular unscented and most off-brand Ultra unscented are just chlorine (sodium hypochlorite and there's also salt) in water. By the way, Clorox Regular is registered with the EPA as a sanitizer and they only registered it for use in pools because that has the bigger market volume. They aren't going to sell that much more bleach by having spa users using it.

Bleach or Chlorinating Liquid + Water --> Hypochlorous Acid + Sodium Hydroxide (sodium ion plus hydroxide ion) + Salt (sodium ion plus chloride ion)

A cost comparison of the various chlorine sources may be found here.

Since you want some CYA in the water, but not too much, then a very reasonable regimen is to use Dichlor initially and then switch to bleach.

If you want to add any other chemicals such as clarifiers, you can always purchase those separately. They do not have to be added "in" a combination chlorine product.

By the way, Sanygen Liquid Shock is just 10.5% Sodium Hypochlorite so is stronger than bleach -- it's chlorinating liquid similar to what you can get at pool stores (though at pool stores it's often 12.5% chlorinating liquid). There is nothing special about it compared to other chlorinating liquid or bleach. There is no such thing as being formulated for spas or to protect covers since ALL chlorine becomes hypochlorous acid in the water. It's true that you wouldn't want to add concentrated chlorine from any source to the cover directly, but there's nothing unique about the different chlorine products in that regard. Sanygen also makes stabilized chlorine tablets that are just Trichlor and are no different from other Trichlor. The only unique formulation of Trichlor is that of BioGuard Smart Sticks which are 96.5% Trichlor with some extra ingredients as "binders" to only dissolve the Trichlor in water when there is water flow so these are safe to put into a skimmer.

I would agree that using a SINGLE source of chlorine will cause problems. If you only used unscented bleach, then the disinfecting chlorine concentration would be too high while if you used only Dichlor then the disinfecting chlorine concentration by the third month may be too low. So understanding the Cyanuric Acid (CYA) level and which products add it is important. Again, it is the ratio of FC to CYA that approximates the disinfecting chlorine level (when CYA is present and at least 5 times higher than FC). At a pH of 7.5, the rough rule of thumb is that this ratio is the equivalent amount of FC if there were no CYA. So, 4 ppm with 20 ppm CYA is roughly equivalent to 4/20 = 0.2 ppm FC with no CYA.

I want to describe some more chemical equivalents. You do NOT have to buy your chemicals from a pool or spa store.

TO MOSTLY RAISE PH:

Sodium Carbonate. This is what is in most "pH Up" products. It raises both the pH and the Total Alkalinity (TA). It is identical to Arm & Hammer Super Washing Soda (careful: not the laundry detergent). It is also known as Soda Ash.

Sodium Tetraborate Decahydrate. This is 20 Mule Team Borax. It raises pH without raising Total Alkalinity (TA) as much. It can also be used as an algaecide if maintained at 30-50 ppm. It is nearly identical to Proteam Supreme (which is Sodium Tetraborate Pentahydrate) except that you need to use 31% more by weight (since Borax has more water content). You use 198% (about double) Borax by weight as Sodium Carbonate.

Sodium Hydroxide. This is a pure base so will raise the pH without as much increase in Total Alkalinity (TA). It is also known as lye or caustic soda and may be purchased where you would buy soap-making products as lye is used in soap. You use 40% as much Sodium Hydroxide by weight as Sodium Carbonate.

TO RAISE ALKALINITY:

Sodium Bicarbonate. This is what is in most "Alkalinity Up" products. It raises the Total Alkalinity (TA) with a small rise in pH. It is identical to Arm & Hammer Baking Soda. Some products call this "Sodium Hydrogen Carbonate" in their ingredients list, but this is just a synonym.

Sodium Sesquicarbonate. This is a 50/50 mix (by molecules; 56/44 by weight) of Sodium Carbonate and Sodium Bicarbonate.

Richard

[Shaamus]

If Sanygen liquid chlorine is not specifically formulated for spas, it would void the cover's warranty then. I wasn't sure since Sanygen does make a couple of spa products.

After rereading Tiny's post, it makes more sense. I thought he had found some 99% effective chlorine and was replacing a 55%, like Leisure Time's Spa 56. But he was switching from an enhanced shock product that is most times MPS + dichlor which makes sense.

[chem geek]

You can write a warranty any way you like, but you are not doing so with an understanding of chemistry if you only allow some chlorine sources and not others. You should be specifying specific water parameters such as pH, Free Chlorine (FC) and Cyanuric Acid (CYA) since pH and disinfecting chlorine levels are what would be most important with regard to the life of a cover. The fact that chlorine came from Dichlor vs. bleach is completely and totally irrelevant.

What exactly do you mean by "formulated for spas"? Is this something some manufacturer told you and if so, who? I've called manufacturers on this sort of thing before and would be happy to get them to clarify this for you.

Richard