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Bleach Vs. Lithium Hypochlorite


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#1 Nat

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Posted 02 January 2008 - 06:36 AM

I've decided I will use a two month interval between water replacement in my spa (I just can not seem to stomach a 3-4 month change interval). At about a month into the current fill, I will test my cyuranic acid levels with a Taylor test kit. I presently use 1.5 tsp. (half a tablespoon) of dichlor prior to using the spa. Its 330 gallons. Use is once every day on weekdays and twice a day on weekends, so I add approximately 5 tablespoons of dichlor per week. My weekly shock is with MPS.

If the CYA level appears high after a month of this routine (and I bet it will be), I would like to switch to using a non-combined chlorine. If its really high, I'll make the switch earlier on my next fill. I've read about using bleach, but I would rather have the convenience of a powder that I can store for long periods. I have found that the bleach I tried as a test during the last fill had lost most of its strength. Lithium hypochlorite seems to fit the bill. Its higher cost is not a concern for me.

Is lithium hypochlorite a good alternative to using bleach as a source of uncombined chlorine? My understanding is that to get the same level of free chlorine, I have to use about twice as much lithium hypochlorite as dichlor, volume wise.

Any opinion?

Thanks.

--Nate

#2 chem geek

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Posted 02 January 2008 - 10:51 AM

Nate,

For every 10 ppm Free Chlorine (FC) you add with Dichlor, it also adds 9 ppm Cyanuric Acid (CYA). 1.5 teaspoons of Dichlor adds about 3.1 ppm FC and 2.9 ppm CYA in 330 gallons so with 5 + 2*2 = 9 doses per week, that is about 26 ppm CYA per week. So I would expect you to measure a little over 100 ppm CYA after a month unless you had some sort of splash-out or dilution from cleaning the filter and replacing some water (or the CYA somehow broke down).

That is surprising that your bleach lost its strength so quickly. Chlorinating liquid that is stronger loses its strength much faster. The table at the bottom of this link gives you some idea of how long a quality product should last. If the bleach is stored at higher temperatures, then it won't last as long but should still take about a year to lose half of its strength. Perhaps it was lower quality bleach with metal contaminants. I know we've had Clorox Regular in our laundry room for over a year and I've tested it and it is still close to full strength (it's stored indoors so at 72F average temperature).

When you say "non-combined" chlorine, I think you mean "unstabilized" chlorine since that is what does not contain CYA in it. You can certainly use Lithium Hypochlorite as it is unstabilized chlorine and is essentially identical to bleach or chlorinating liquid in its effects (i.e. it doesn't add anything extra except some salt). It is a fast-dissolving powder and its only downside is the cost so if you don't care about that then it certainly is an option for you.

Whereas Dichlor (dihydrate, the most common form) is 55.4% Available Chlorine (relative to 100% for chlorine gas), Lithium Hypochlorite is 35.2% so you need 55.4/35.2 = 1.57 times as much Lithium Hypochlorite by weight to get the same FC level. The density of Dichlor Dihydrate is around 0.985 g/ml in bulk while Lithium Hypochlorite is also similar at 0.98 g/ml bulk density. So the rough rule of thumb is that you need to use 60% more Lithium Hypochlorite by weight or volume to get the same FC as Dichlor.

Richard

#3 B0Darc

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Posted 02 January 2008 - 11:24 AM

You know those V8 vegetable juice commercials where the folks are not eating their vegetables and get a clonk on the head (coulda hadda V8?)

Doncha just wanna clonk yourself on the head ">TwOnK!< ...coulda paid more attention in Chemistry class!" rolleyes.gif

Thanks chem geek!

Bo "when am I *ever* gonna need to know how to calculate mole weight in real life?" Darc

#4 lmartine

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Posted 02 January 2008 - 11:56 AM

I tried lithium chloride for a while, I found it really hard to dissolve (even stirring madly in my 1l jug of warm spa water). In my area it is probably about 4 times the cost of dichlor when you take into account the lower chlorine concentration.

I have heard calcium chloride is to be avoided since it adds calcium, does lithium affect 'hardness' as well?

Liquid bleach can save a round trip out to the spa (-27C with the wind today) to fetch some warm water, but I usually need some water to test anyways.


#5 Nat

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Posted 02 January 2008 - 12:07 PM

Thanks. That's exactly the answers I was looking for. I think I'll try some lithium hypochlorite and see how well it works and disolves for me.

I also wanted to know how much the CYA increased per how much dichlor I was adding and Richard's answer provides that. More than I thought!

I can't imagine how much CYA some people have in their spas at the end of 4 months, using strictly dichlor for both clorinating and shocking the tub, and I am sure some people will use more dichlor than is necessary!

Also, part of the problem in using bleach is that I bleached my shirt acidently and my wife is happy with me using it. It just seems easier to use a powder. The bleach I was using was a no-name brand that could have been sitting around a while. I could get the chlorine up, but it took about twice the amount recommended on this discussion group.

Thanks again.

--Nate

#6 B0Darc

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Posted 02 January 2008 - 12:08 PM

QUOTE(lmartine @ Jan 2 2008, 01:56 PM) <{POST_SNAPBACK}>
I tried lithium chloride for a while, I found it really hard to dissolve (even stirring madly in my 1l jug of warm spa water). In my area it is probably about 4 times the cost of dichlor when you take into account the lower chlorine concentration.

I have heard calcium chloride is to be avoided since it adds calcium, does lithium affect 'hardness' as well?

Liquid bleach can save a round trip out to the spa (-27C with the wind today) to fetch some warm water, but I usually need some water to test anyways.

I was one of the people that started using Cal-Hypo (calcium hypochlorite instead of sodium or lithium) and yes it adds alot of calcium over the period of 3 month lifecycle. This could be a good thing if your Calcium hardness was low, but it also did not dissolve well for me (HTH brand).

#7 chem geek

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Posted 02 January 2008 - 12:22 PM

QUOTE(lmartine @ Jan 2 2008, 11:56 AM) <{POST_SNAPBACK}>
I tried lithium chloride for a while, I found it really hard to dissolve (even stirring madly in my 1l jug of warm spa water). In my area it is probably about 4 times the cost of dichlor when you take into account the lower chlorine concentration.

I have heard calcium chloride is to be avoided since it adds calcium, does lithium affect 'hardness' as well?

Liquid bleach can save a round trip out to the spa (-27C with the wind today) to fetch some warm water, but I usually need some water to test anyways.

Lithium Hypochlorite does not add to calcium hardness. Only Cal-Hypo (Calcium Hypochlorite) does that. For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by 7 ppm.

That is strange that you found Lithium Hypochlorite to dissolve slowly. It is supposed to dissolve quickly (I've never tried it myself, however, so maybe this is yet another industry "myth"). Perhaps it wasn't powdered enough in the brand you bought. By comparison, Cal-Hypo is known to dissolve slowly.

As for cost comparison against Dichlor, see this link for a cost (for equivalent chlorine) comparison of chlorine sources including the "hidden" cost of the extra pH Up product needed for the acidic sources of chlorine.

Richard

#8 B0Darc

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Posted 02 January 2008 - 02:45 PM

QUOTE(chem geek @ Jan 2 2008, 02:22 PM) <{POST_SNAPBACK}>
QUOTE(lmartine @ Jan 2 2008, 11:56 AM) <{POST_SNAPBACK}>
I tried lithium chloride for a while, I found it really hard to dissolve (even stirring madly in my 1l jug of warm spa water). In my area it is probably about 4 times the cost of dichlor when you take into account the lower chlorine concentration.

I have heard calcium chloride is to be avoided since it adds calcium, does lithium affect 'hardness' as well?

Liquid bleach can save a round trip out to the spa (-27C with the wind today) to fetch some warm water, but I usually need some water to test anyways.

Lithium Hypochlorite does not add to calcium hardness. Only Cal-Hypo (Calcium Hypochlorite) does that. For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by 7 ppm.

That is strange that you found Lithium Hypochlorite to dissolve slowly. It is supposed to dissolve quickly (I've never tried it myself, however, so maybe this is yet another industry "myth"). Perhaps it wasn't powdered enough in the brand you bought. By comparison, Cal-Hypo is known to dissolve slowly.

As for cost comparison against Dichlor, see this link for a cost (for equivalent chlorine) comparison of chlorine sources including the "hidden" cost of the extra pH Up product needed for the acidic sources of chlorine.

Richard

Nice thread there Nat...
Basically you want to switch to lithium because it's powder and that's convenient. When I tried to visualize chemically how they made Lithium Hypochlorite into a solid, it made me wonder. The expense I'm sure comes from manufacturing, as Lithium is like Sodium (and pure potassium!) soft and explosively reactive metals where water is concerned... which is how it's manufactured. Pure forms of these metals are usually stored in kerosene as they want to combine so fiercely with water that they will pull moisture right out of the air. In the case of sodium, that makes lye and hydrogen so the kerosene insulates that reaction from occurring which could obviously be problematic. Can you say boom? So after carefully mixing the sodium and water to make lye next they bubble chlorine through the lye solution to make bleach. Anhydrous lye (dry) is also very reactive, it's known as drain cleaner... something no one is putting in their hottub

Of course none of this is happening in your spa! It's all happening down at the chemical plant that I am glad I don't work at ph34r.gif I am just wondering about the level of reactivity is in powdered Lithium Hypochlorite... so I looked it up. I'm not talking about toxicity as lithium is elementally the sister to sodium and potassium. I'm referring to what you know about Sodium Hypo (just a 6% solution in bleach) from spilling some on your shirt. Turns out Lithium Hypo is very common commercially <click me>

It also turns out to be available as a liquid, I have to guess that is much cheaper. Hmm it says it's used to sanitize dairy equipment... maybe you could get some at the feed store? Or online from a non-pool source. As long as you are getting a preparation targeted for food source use it should be the same (purity). My question was... do they have to add something to it to get it to a powdered form (solid)? I would expect it to be extremely soluble! Be careful not to let any water get in the canister of solid material. My next question was if they can make solid Lithium-Hypo, can they make solid Sodium-Hypo? Any price difference? See I just put these questions in chem geeks head and he also must know the answer. The goal being getting the cheapest easiest chlorine in our spas.

#9 chem geek

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Posted 02 January 2008 - 04:41 PM

Lithium Hypochlorite is manufactured in a similar way as Sodium Hypochlorite except that some of the Sodium Hydroxide (lye) that is used is replaced with Lithium Hydroxide instead. The pure metals of sodium and lithium need not be (and are usually not) involved at all in the manufacturing process. The manufacture of Sodium Hypochlorite is described in this link and you can lookup the chlor-alkali manufacturing process for much more information. Essentially, the chemical process is as follows and just uses salt from evaporated sea water -- no need for any solid sodium metal at all. It is the simple electrolysis of chloride ion and hydrogen ion (that is, salt water) that is done. It is essentially the same thing that happens in a saltwater chlorine generator (SWG) for pools except that the SWG concentrations get hugely diluted via pumped water.

Anode: 2Cl- --> Cl2(g) + 2e-
Cathode: 2H2O + 2e- --> H2(g) + 2OH-
----------------------------------------------------------------
Net Reaction: 2Cl- + 2H2O --> Cl2(g) + H2(g) + 2OH-
Chloride Ion + Water --> Chlorine Gas + Hydrogen Gas + Hydroxyl Ion

Notice that sodium has nothing to do with the above reactions and in fact lithium can be used instead for the salt (LiCl instead of NaCl). The above reaction written with sodium could be seen as follows.

2NaCl + 2H2O --> Cl2(g) + H2(g) + 2NaOH
Sodium Chloride (salt) + Water --> Chlorine Gas + Hydrogen Gas + Sodium Hydroxide (lye)

The Chlorine Gas is then mixed with the Lye in water to produce Sodium Hypochlorite and this is usually done separately for higher purity and lower salt content (rather than doing so in one step in the electrolytic cell).

Cl2(g) + 2NaOH --> NaOCl + NaCl + H2O
Chlorine Gas + Sodium Hydroxide (lye) --> Sodium Hypochlorite + Sodium Chloride (salt) + Water

One can certainly try to evaporate the water in the resulting Sodium Hypochlorite solution and can produce Sodium Chloride salt plus Sodium Hypochlorite Pentahydrate (NaOCl•5H2O) which is a solid, but is VERY unstable. This is why it is not sold commercially. It is far too reactive and unstable.

The net result of the entire process from beginning to end (using electrolysis to provide the energy to drive the reaction) is

NaCl + H2O --> NaOCl + H2(g)
Sodium Chloride (salt) + Water --> Sodium Hypochlorite + Hydrogen Gas

Lithium Hypochlorite can be produced by substituting Lithium Hydroxide for some of the lye in the above as in

Cl2(g) + NaOH + LiOH --> LiOCl + NaCl + H2O
Chlorine Gas + Sodium Hydroxide (lye) + Lithium Hydroxide --> Lithium Hypochlorite + Sodium Chloride (salt) + Water

Then through evaporation of the water one is left with solid Lithium Hypochlorite and Sodium Chloride (salt). Lithium Hypochlorite is relatively stable. The salt content in Lithium Hypochlorite is virtually identical to its content in Sodium Hypochlorite (chlorinating liquid or bleach). For every 10 ppm Free Chlorine (FC) you also get 8 ppm salt (in sodium chloride units as "ppm" is a weight measure).

Unfortunately, solid Sodium Hypochlorite is unstable so your only hypochlorite choices are Lithium Hypochlorite which is stable but expensive or Calcium Hypochlorite (Cal-Hypo) which adds to Calcium Hardness (CH) or Dichlor and Trichlor which add to Cyanuric Acid (CYA). Potassium Hypochlorite is a liquid so there isn't any benefit to it over Sodium Hypochlorite and would be more expensive since Sodium Chloride salt is the most inexpensive and readily available. Other than on-site generation of hypochlorite in an SWG, there is no dense inexpensive source of chlorine that does not add extras you don't want to build up (i.e. CYA or CH). Chlorine gas is pure, but is not dense and is very dangerous in its concentrated form (it is used in some commercial pools).

Richard

#10 B0Darc

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Posted 03 January 2008 - 06:44 AM

That clears up that question! So that's why bleach is so cheap. Dry Lithium hypo sounds intriguing. I bet it's available in bulk for a (more) reasonable rate. Man they must make a fortune selling bleach, it must cost like a penny a gallon to manufacture. Another case of the bottle costing more than the contents!

THANKS FOR THE BREAKDOWN chem geek, it's actually very interesting!

#11 B0Darc

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Posted 03 January 2008 - 07:11 AM

Pardon my fascination, but the manufacture of bleach is so simply goofy I am amazed. Now other than the extreme explosive and toxic nature of creating free chlorine and free hydrogen it is amazingly easy. To *oversimplify* you pass electricity through salt water and the sodium (Na) and chlorine (Cl) split and recombine with the water (H-OH or H2O) to make NaOH (lye) and free chlorine and free hydrogen. Then you bubble the free chlorine back through and you make bleach. Forgive the leaving out of all the details... like what do you do with all that hydrogen (pump it to fuel cells to make the electricity needed to make more bleach!) and all the safety you need when handling pure chlorine gas, and all the membrane technology needed to electrolyze salt water... but I feel an invention coming on... like Mr. Coffee®? Mr. Bleach. Whadda ya say chem geek, me and you hombre. Every spa should have it's own Mr. Bleach®! (hahha) and I bet mrbleach.com is not taken. <insert me taking credit for the miniaturization of the bleach manufacturing process for home pool and sap use here>

...engh another million dollar idea down the drain cool.gif

#12 chem geek

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Posted 03 January 2008 - 07:41 AM

Just remember that the sodium and chloride in salt were "split" when the salt dissolved in the water to produce separate sodium and chloride ions. The electrolysis has nothing to do with the splitting so the fact that the salt had sodium vs. lithium vs. potassium vs. calcium vs. magnesium is irrelevant for the electrolysis and production of chlorine gas. It's the chloride ion that is what matters. I know that a lot of websites that talk about SWGs and electrolysis talk about splitting sodium and chloride, but that's just bunk. They are already split through dissolving salt in water. Yes, when you dissolve soluble solids in water you are splitting the molecule (well, actually it's the water that is doing the work, but you can certainly take the credit!). Some compounds (mostly liquids) are already polar (have large separation of charge) so mix with water without splitting (e.g. alcohol) while others are not so do not mix (e.g. most oils).

You can actually buy a relatively inexpensive SWG from Intex (see here, for example) that is designed for above-ground pools and could use a smaller version for a spa though I've never heard of one. However, don't forget that you need the water to be salty for the SWG to produce chlorine -- usually around 3000 ppm is the minimum recommended amount. Salt water is more corrosive (due to its conductivity, chloride interference with stainless steel passivity layer reformation, and salt evaporation/recrystallization pressure in stone) than less salty water so you do need to be careful about the types of materials you use around an SWG system (see this link for one side and this link where I try to understand what's going on -- most users with SWG pools don't experience such problems so quickly, but some do).

Richard

#13 Chris W

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Posted 03 January 2008 - 07:17 PM

Autopilot has a small SWG for Spas, called the Spa-Pilot.

http://www.autopilot...t/spapilot.html

The literature states 1800-2200 ppm salt, but an Autopilot rep quoted an even lower number on another forum when it 1st came out.

I was looking at one before X-mas, but I was hoping to hear reports from other before I tried it

I was ready to launch on one but I'm not sold on the power-pouches befaore and after each use. It seems like if I need to add chems every time I use it, I might as well add bleach too.

Back on topic, I've looked for Litium Hypo, but haven't found it locally. Does anyone know of a common brand?

Chris W

#14 B0Darc

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Posted 04 January 2008 - 12:18 PM

Thanks you guys! We are way off topic, but all good stuff. My search for lithium-hypo took me to an online patent for a new production technique registered to the Olin corporation. When I went to their site it seems their consumer pool chemical line had been sold to Arch Chemicals... who owns the whole shooting match! ...we may never see cheap lithium hypochlorite. Interesting though it's also been approved as a pesticide. So take a peek over at these guys..

http://www.archchemi...ucts/water.htm/

Yeah you still have to add something (powder packs?) to restore the chlorine to the buffer for the SWG spa thingy (Autopilot) and bleach is just so darn cheap instead. yeah my Mr. Bleach idea was more like an independent generator for chlorine where you just added salt instead of coffee beans (heh) and to heck with making bleach when all you want is the chlorine... We'll just call it Mr. Chlorine! ..and I do get the SWG principle ...the whole spa becomes a Mr. Chlorine, brilliant.

#15 B0Darc

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Posted 04 January 2008 - 12:20 PM

.

#16 chem geek

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Posted 04 January 2008 - 01:54 PM

You actually don't need to add any more salt once you've added it because the chlorine becomes chloride (salt) after it gets used up. So the SWG essentially converts salt (chloride) to chlorine which then kills pathogens or oxidizes organics or ammonia or breaks down in sunlight and gets converted back to salt (chloride) so you generally do not run out of salt and don't need to add more (except for splash-out or backwashing, as in some pools).




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