Artesian Island Spa Series Grand Cayman Technichlor Corrosion

[Maastricht]

Hello all,

Hope you could help me with a corrosion problem at a an full options Artesian Island Spa series Grand Cayman using a Technichlor salt water generator. The spa is almost new, delivered at August 15th 2012.

Let me first explain our specific situation:

• We live in The Netherlands.
• We are a family of 2 adults and 2 children (3 and 1 year old)
• We would like to use the spa on average with 2 adults 2-3 times one hour per week. When our children will get older we plan to use the spa also more often with them.
• Sometimes we will invite friends. There are 6 seats so it could be happening that we will use the spa with 6 adults. This will be a maximum of a few times a year.
• The spa is situated outdoor but under a roof. (almost no UV sunlight)
• My wife and I both work fulltime and we bought the spa for relaxation mostly at night. Due to our busy schedule and also many times that we are travelling for a few days we would like to keep the water chemistry as simple as possible.
• The water hardness of our tap water is 150 PPM.

When we ordered the spa our dealer didn’t recommend to use a ozonator while it would affect the lifetime of the pillows and cover. So we didn't add this option.

Please allow me first to explain why we made some choices in the past: (of which many were influenced by information I found on this forum)

Our dealer recommended us to use only Melpool 90/20 (based on Trichlorine) or to use bromine. We don’t want to use these chemicals please allow me to explain why…

Trichlorine:

Under the brandname Melpool 90/20 20 gram slow dissolving tabs are being sold on the Dutch market. These tabs contain Trichlorine and cyanuric acid. Our dealer explained that we should add one or two tabs into a floating feeder during a week. My first problem is the warranty limitations and exclusions of Artesian which state:

“Unapproved sanitizers such as calcium hypochlorite, sodium hypochlorite, "tri-chlor" type chlorines or any sanitizing chemical that may remain undissolved on the spa surface, or damage caused by failure to provide level and complete support to the spa, or damage caused by not properly preparing the spa for the winter.”

The second problem is cyanuric acid which is builds up. I have made my own calculation and after 3 months I end up with levels of 73 PPM of cyanuric acid but I only counted with 1 tab of 20 grams per week and no shocks! In reality this could easily also be the double because I am not using an ozonator. Levels of cyanuric above 70PPM are exceeding recommended levels 30-50PPM and time to kill bacteria will rapidly increase.

I also have spoken with Melpool. They tell me not to use Trichlorine in a spa because it is acid (PH2,9) and could cause corrosion and destroy your pillows. The great advantage is that the tablets are slow dissolving in the floater which gives us the benefit to leave home for a few days without having to worry about free chlorine levels falling to a zero level.

Due to the given facts above we don’t prefer to use trichlorine. We do want to mention that our dealer explained to us that he has sold about 900 spas within The Netherlands and that almost all of these customers are using Melpool 90/20 without any problems. What is your opinion?

Bromine (Hydrotech or Lonza):

Another factory recommendation is bromine. Bromine is not approved in The Netherlands. We could buy it in another European country like Belgium for example. When I did some research on the internet I found some sources which link the use of bromine on long term to damage of the human nerve system. This don’t give us a positive feeling especially while our kids are in the spa too. This was also the reason we didn’t order the ISIS bromine generator as an option. The advantage of bromine would be that we could go away for a few days without having to worry about our free bromine level due to the dispenser which holds a buffer of bromine tablets. Our dealer told us that bromine is not approved in The Netherlands because an approval costs a lot of money.

When I read the Artesian manufacturer manual carefully the usage of two sanitizers are allowed and will not void any warranty:

- Sodium Dichlor

- Bromine (Hydrotech or Lonza) (already explained above)

Sodium dichlor:

Ok, back to the factory recommendations. Dichlor is usually sold in granular form and PH neutral (6,9). I did find a few companies which are approved by Dutch authorities who sell very small tablets of 2,7 gram (sodiumdichlorisocyanuric 55%) so you are able to dispense these tablets via a dispenser. Also dichlor adds cyanuric acid but even in a greater extend then Trichlor. Our dealer explained before we bought the spa that we would only need to drain the spa every 3 months. When I do my calculation again I would end up after three months at a level of 112PPM, which is also far above healthy levels.

In reality this could easily be the double because I am not using an ozonator and I also didn’t count any shocks. Giving in mind that levels of cyanuric above 112PPM are exceeding recommended levels 30-50PPM and time to kill bacteria will rapidly increase and I would like to use my water for about three months this chemical wouldn’t not be an option too. Furthermore the down side of dichlor is that it will not sustain a FC PPM level for long time in hot water due to its very fast dissolving.

Ok, what would be other options then in our opinion but which could interfere with guarantee:

Chlorine gas

Could be an option but is far too complicated for private use.

Sodium Hypochlorite (liquid bottled form)

Popular at a lot of forums like the www.poolspaforum.com The downsides are in my opinion, sodium be added to the water which could cause corrosion. Shelf life should be very short while the strength will rapidly decrease. High PH (13,0). Again we are not able to leave home for a few days while the FC falls rapidly to zero.

Calcium Hypochlorite

Adds 0,7PPM calcium for every 1PPM of chlorine. Due to the fact our tap water has a water hardness of 150 PPM I estimate that we will end up at a total water hardness of 230 PPM after three months. But again I haven’t calculated any shocks and possible the amount of calcium hypochlorite we should use is higher so we will end up higher let’s say around 300 or 350 PPM. Artesian states levels above 250 PPM could cause scale forming. I am aware of the Langelier saturation index and to my calculations there should not occur any scaling when you are keeping the pH stable at 7,4. While these calcium hypochlorite tabs are quickly dissolving too we have the problem again of FC levels falling rapidly and we are not able to go away for a few days without coming back and see a FC level above zero.

This brought me to two options to solve all the issue above:

Combination of dichlor and calcium hypochlorite:

After water refreshment we start with maximum 3 weeks of dichlor, which will add cyanuric acid to a level of about 28 PPM. Then switch over to HTH calcium hypochlorite and we will end up at a water hardness of 207 PPM at least but more probably around 270 PPM after 3 months. The main disadvantages for us are, many different chemicals, the need of a logbook, complexity due to the Langelier Saturation Index calculations, adding more times chlorine to the spa during one week and when we are away for a few days we still have the great disadvantage the FC level easily falls down to zero.

SWG (Salt water chlorine generator):

The only disadvantage is you need to add 2000PPM of natrium/salt. Before we started we asked our dealer for his advice and Balboa too because we were afraid that the stainless steel heater could start to corrode due to the added salt. Balboa said that the SS heater is not made for salt water systems and that a titanium heater would have a much longer lifetime. Our dealer also explained that this is the reason why Artesian offers a titanium heater in combination with the ISIS salt system. We asked our dealer too if we could end up with corrosion at our spa jets. He explained to us that he can’t guarantee anything but that corrosion at stainless steel jet covers due to a salt level of 2000PPM would be unlikely. He stated that the same standard stainless steel jet covers are being used for the ISIS system too. Besides this our dealer has one other customer within The Netherlands which uses an INTEX salt water chlorine system with his Pelican Bay until today without any corrosion problems

Sorry, it’s such a long story but we decided to go for the 2nd option at October 16th. Our dealer told us this decision would be at our own risk but we felt we didn’t have any other water chemistry option left what would fulfill the promises when we made the decision to buy the spa in the beginning. (water replacement every 3 months, adding chorine tab once a week, so less work) Therefore we have ordered the Technichlor of the company Controlomatic (http://www.controlomatic.com/) via a Dutch dealer. The Technichlor is very easy to use, temperature compensated, chlorine production is programmable and has a boost modus for extra chlorine adding after hot tub usage. The Technichlor will produce a constant chlorine level during our absence so we are finally able to go away again without any worries. The power level is selectable on a scale of 1 to 10.

According to the manual we have selected power level 6 which should be the right level for a spa of 400-500 gallons. Our Grand Cayman is a 475 gallon spa. We ordered a titanium heater at our dealer too as part of preventive maintenance.

November 8th 2012, so only after two months almost all jets suddenly got corroded after a short 5 day holiday. Before our holiday I checked the PH and made sure it was at a level of 7,4 and when we came back the PH was 7,56. I measure PH and Redox/ORP via a digital Hanna Instruments meter which is calibrated each month and very accurate. I am 100% sure that the PH never went out of the 7,3-7,7 range during the 2

months that I used the SWG. I have checked PH at least 3 times a week. I am very confident the FC level never exceeded 5PPM while I measured this not only indirect via ORP but via test strips too. Most of the corrosion started at the back of stainless steel jets covers:

<I notice that adding attachments is not very easy, I will uploaded them afterwards>

I drained the spa completely and removed all jets. Then I removed all SS covers on the pictures you will find only a part of the 60 jets that got corroded.

Then I cleaned all plastic jets with a grinding sponge. Most stainless steel covers are damaged. (pitting)

While I had to wait for a long time for the titanium heater I didn’t had time to change the old “SS” heater yet. I disassembled everything after the vcorrosion occured and found absolute no corrosion in the SS heater.

What I did find very strange is bubbles at the upside of the filter.

After consulting Artesian (manufacturer and dealer) they actually state that a SWG would be "deadly" for their hot tubs and we should use bromine or dichlor which have specific disadvantages which we explained above. Also after the heater modification of stainless steel to titanium. Controlomatic guessed our water hardness was not ok or I generated to much chlorine.

Therefore I decided to give it another try at december 27th 2012. I started this time with a water hardness of 150PPM. This time I also started with dichlor to build up a CYA level of 30PPM which should make the chlorine less aggressive. I used dichlor until the 23rd of January. Then I added 2300gram of salt with a purity of 99,9% without iodine. (which is also much less then what I added the first time when things went wrong. (this was 2900gram) Yesterday the 16th of February I noticed again corrosion at the back side of our SS jet cover. This time I only mounted three new SS jets all other jets were mounted without any covers. All measurements during the 2nd try were again with our digital Hanna meter for PH, which was always between 7,6 and 7,8 and very stable. This time I didn't use any ORP values anymore but used DPD1 tablets and measured always between 0,5 and 4PPM. I measured almost every day and noted all the values.

What am I doing wrong? I hope someone is willing to help us.

[Maastricht]

Hello all,

<I notice that adding attachments is not very easy, I will uploaded them afterwards>

I am trying to add pictures to the story but I don't succeed. Can someone please explain how this works?

On the pictures you can see all the corrosion on the back side of the SS covers which are mounted over the plastic jets. You can also see all jets disassembled. You can see the "old" stainless steel heater without any corrosion and the original filter which started to bubble at the upper side. This mainly pointed on an excess of chlorine the dealer stated. He had seen this same phenomenon at other customers which had their trichlorine floater within the filter basket. Therefore I tried it a 2nd time and monitored the chlorine level daily which was always between 0,5 and 4PPM.

Last but not least from december 27th 2012 we only used the tub for 3 hours in total. We did this especially while I wanted to get good measurements and a consistent chlorine level as possible while during the first try the corrosion already occured after 3 weeks which is actually comparable with this 2nd try while we used dichlor until the 23rd of January and discovered corrosion at the 16th of February again.

Thanks in advance for your help!

[Maastricht]

Hello all,

Maybe the information above was overwhelming...

If I may summarize my questions of which I hope you are willing to provide us some feedback:

• Should you consider the use of trichlorine within a hot tub?
• Do you have an explanation for corrosion at new SS jet covers due to SWG system within only 3 weeks? (1st try with 2900 gram (about 2000 PPM) and 2nd try with 2300 gram (about 1600PPM) of salt at an 475 gallon hot tub) Free chlorine level was always within 0,5 and 4PPM.
• Assume we leave all SS covers of the jets (not very aesthetical but anyway) would you guess other parts will start to corrode to? We have changed preventively the standard Balboa SS heater into a titanium heater already.
• Do you have any other suggestions low maintenance water sanitizing methods? (Bromine is not allowed in The Netherlands)

Thanks in advance for your help!

[chem geek]

First of all, let's clear up some misconceptions. ALL sources of chlorine will increase the salt level because the chlorine when used up becomes chloride. Dichlor adds sodium while Trichlor effectively does because you need to add something to compensate for its low pH and that it decreases TA so you usually end up adding sodium carbonate (pH Up) or sodium bicarbonate (Alkalinity Up) both of which add sodium. So bottom line, you add sodium chloride salt with ANY source of chlorine that you use.

Now it is true that with sodium hypochlorite you add twice as much salt because there is already sodium chloride in that product. The following are chemical facts independent of concentration of product or of pool/spa size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm and after pH adjustment it increases salt by 8 ppm.

For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm and salt by 8 ppm.

For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm and salt by around 10-12 ppm.

For every 10 ppm FC added by sodium hypochlorite or lithium hypochlorite, it increases salt by around 17 ppm.

As for using Trichlor, it usually isn't used in spas because it is very acidic and usually dissolves too quickly at hot spa temperatures. However, it sounds like they may have a special floating dispenser that limits the dissolution rate. So long as you are managing the pH and don't let it get too low, then using Trichlor is OK, BUT try to have the feeder positioned near the center of the spa and not next to the edge. If there is no circulation at times, then the pH near the feeder will get very low and rust components near it.

Unless the stainless steel is of poor quality, it shouldn't degrade that fast. Nevertheless, higher salt levels do accelerate metal corrosion, BUT I think the real issue in your case is that you used the SWG without initially having any CYA in the water. The chlorine is way, way too strong in that case so the combination of high salt level and high active chlorine level vastly accelerates metal corrosion. The fact that you still see it after adding CYA probably has more to do with the fact that you've already started SS corrosion and once started it will continue to corrode even at lower salt and chlorine levels. You'd need to resurface (smooth) it to create a new chromium oxide protective surface layer. Yes, SS is somewhat self-healing, but only to some extent and if you get rust spots they need to be sanded away.

Using a titanium heater is a good idea regardless since it is far more corrosion resistant.

Why aren't you using the Dichlor-then-bleach method? It has no CYA buildup (except the intentional initial buildup) and has the water last at least twice as long as Dichlor-only. It does build up salt, but starts out at a lower level so on average isn't very high -- at double the normal Water Replacement Interval (WRI) with daily use it would be around 1000 ppm salt added. The main downside is that it's a manual approach requiring adding chlorine after every soak and in between soaks if you don't soak every day or two. If you go with this approach, lower the TA to around 50 ppm and add 50 ppm Borates -- unfortunately this will be difficult in Europe since boric acid is nearly banned for use. Too bad, because it's only issue is in concentrated form, not diluted. You could alternatively use a phosphate pH buffer, but it will precipitate calcium so can be messy upon addition (especially in the filter).

As for low maintenance, the Technichlor is a good option, but I'd use the minimum amount of salt needed to produce chlorine and I would use more CYA -- perhaps around 50 ppm would be a decent target. If you wanted to use the Trichlor feeder instead, you could do that but have to manage the pH and try and position it away from spa surfaces (tether it somehow, perhaps with a cord going across the spa when you close the cover or something like that).

[Maastricht]

Hello Chem Geek, thanks for your reply! I read many of your posts in the past which are always very impressive. I will try to provide some more feedback in red.

First of all, let's clear up some misconceptions. ALL sources of chlorine will increase the salt level because the chlorine when used up becomes chloride. Dichlor adds sodium while Trichlor effectively does because you need to add something to compensate for its low pH and that it decreases TA so you usually end up adding sodium carbonate (pH Up) or sodium bicarbonate (Alkalinity Up) both of which add sodium. So bottom line, you add sodium chloride salt with ANY source of chlorine that you use.

Now it is true that with sodium hypochlorite you add twice as much salt because there is already sodium chloride in that product. The following are chemical facts independent of concentration of product or of pool/spa size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm and after pH adjustment it increases salt by 8 ppm.

For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm and salt by 8 ppm.

For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm and salt by around 10-12 ppm.

For every 10 ppm FC added by sodium hypochlorite or lithium hypochlorite, it increases salt by around 17 ppm.

As for using Trichlor, it usually isn't used in spas because it is very acidic and usually dissolves too quickly at hot spa temperatures. However, it sounds like they may have a special floating dispenser that limits the dissolution rate. You are correct our dealer provides "special" floating dispenser which are able to regulate the chlorine level to a certain level. So long as you are managing the pH and don't let it get too low, then using Trichlor is OK, BUT try to have the feeder positioned near the center of the spa and not next to the edge. We use EVA foam which floats on the spa water. We could make a hole in the middle so that the floater would always stay centered. I don't know if EVA foam is common in the US, but in Europe due to high electricity rates, we try to isolate everything the best we can. Our spa uses on average about 5-6kWh per day (heating and filterpump). Which means about $1,60-$2 per day. When I use the spa on my own I leave to foam on the water and only turn back the part where I sit. If there is no circulation at times, then the pH near the feeder will get very low and rust components near it. In my opinion the disadvantage of trichlorine is the effect on PH (especially while we aren't able to buy borates), hard to reach consistent chlorine levels, build of CYA which result in early water replacement and the void of factory warranty.

Unless the stainless steel is of poor quality, it shouldn't degrade that fast. According to Artesian the SS covers are made of SS316. I doubt that statement. My personal opinion is SS304 which is low grade quality. Nevertheless, higher salt levels do accelerate metal corrosion, BUT I think the real issue in your case is that you used the SWG without initially having any CYA in the water. You are correct the first attempt was without any CYA in the water. The chlorine is way, way too strong in that case so the combination of high salt level and high active chlorine level vastly accelerates metal corrosion. The fact that you still see it after adding CYA probably has more to do with the fact that you've already started SS corrosion and once started it will continue to corrode even at lower salt and chlorine levels. This is not completely correct. The 2nd try I added 30PPM of dichlor by using dichlor for about 4 weeks. (FC level never exceed 4PPM) I also mounted 4 brandnew SS jets of all other jets I removed the SS covers. My idea behind this was to try this for 6 months and then replace all jets when the corrosion wouldn't come back anymore. I need to replace the complete jets while they factory doesn't sell the SS covers only. Of the 4 brandnew SS jets, 2 SS covers corroded again 3 weeks after adding the salt. Everytime when corrosion occurs it happens at the back side of the SS covers. The back side is matte and the front side is polished.

For me it's still unclear if the corrosion occurs due to the salt or the chlorine. Therefore I also started a vase "experiment". I added 2 liters of water in a vase and added only salt (no chlorine) even 3 times the level (4800PPM) of which I use in our spa. I used a brandnew SS cover again. This cover was not mounted on the jet so I was able to easily notice when corrosion would start. After 3 weeks still no visible corrosion. Then I added 3 times half a 2,7 dichlor tablet which should really result in high chlorine levels. Totally against my expectations to corrosion occured. The undissolved chlorine tablet even laid down directly on the SS matte surface. The only difference is that the spa is heated to 38 degrees Celcius and the vase was in our garage at around 5 degrees Celcius. I guess we need your Mythbusters here in The Netherlands. ;-) You'd need to resurface (smooth) it to create a new chromium oxide protective surface layer. Yes, SS is somewhat self-healing, but only to some extent and if you get rust spots they need to be sanded away.

Using a titanium heater is a good idea regardless since it is far more corrosion resistant.

Why aren't you using the Dichlor-then-bleach method? It has no CYA buildup (except the intentional initial buildup) and has the water last at least twice as long as Dichlor-only. I understand the method but the 1st disadvantage is for us that I a frequent traveller and because my wife doesn't want to do any water maintenance, I need to find a method which cares for itself during the days that I am away from home. 2nd disadvantage is I went to our grocery store to find sodium hypochlorite. They don't sell the Clorox brand. They only sell a product which contains sodium hypochlorite <5% and which has some addtives added. The additives are not named in detail, so you don't know what you add to your water. It does build up salt, but starts out at a lower level so on average isn't very high -- at double the normal Water Replacement Interval (WRI) with daily use it would be around 1000 ppm salt added. The main downside is that it's a manual approach requiring adding chlorine after every soak and in between soaks if you don't soak every day or two. If you go with this approach, lower the TA to around 50 ppm and add 50 ppm Borates -- unfortunately this will be difficult in Europe since boric acid is nearly banned for use. This was actually the 3rd disadvantage. You are right we are not able to buy borates here. Our government links this product to cancer, just like the usage of bromine. I was afraid that the dichlor then bleach method would influence our PH to much. Today with the Technichlor my PH stays always around 7,6-7,7. I measure digital with a calibrated and temp. compensated Hanna meter. Our TA is on the low side. I haven't measured it last week but I expect today somewhere around 40-50PPM. Too bad, because it's only issue is in concentrated form, not diluted. You could alternatively use a phosphate pH buffer, but it will precipitate calcium so can be messy upon addition (especially in the filter).

As for low maintenance, the Technichlor is a good option, but I'd use the minimum amount of salt needed to produce chlorine and I would use more CYA -- perhaps around 50 ppm would be a decent target. With the dichlor-then-bleach method you recommend 30PPM. I understand the possible corrosion advantage of a CYA level of 50PPM but are there also disadvantages of CYA at 50PPM? If you wanted to use the Trichlor feeder instead, you could do that but have to manage the pH and try and position it away from spa surfaces (tether it somehow, perhaps with a cord going across the spa when you close the cover or something like that).

Yesterday evening I used the spa with a friend and started with FC around 4PPM. After an hour I turned the Technichlor (powerlevel 6) into boost mode and left the spa. This morning I measured FC 2PPM again. Therefore I am satisfied about this device. The only problem which frustrates me is the SS corrosion of the jets. Maybe I will just leave all the SS covers of the jets while the advantage of the SWG for my usage is greater then the aesthetical advantage of the SS covers on the jets.

Do you expect the salt water can damage more internal parts in the spa? I replaced the heater for titanium but can't check the pump axles for instance. Artesian told me never to use salt water while they tried an trashed many spas. On the other hand the also sell/sold the ISIS system which is a bromine salt generator. It's my feeling that a SWG is almost the same, but I don't know if there were other corrosion sensitive parts replaced when a customer would choose the ISIS system. What would be your personal feeling?

Thanks in advance for your help!

[chem geek]

I think 50 ppm will be fine. It only somewhat lowers the active chlorine level, but mostly when you go into boost mode it keeps things a bit more in check. It's still much lower than typical Dichlor-only users after a few weeks.

Interesting experiments you did, though as you indicated temperature is a factor. I wonder, though, if you might have some sort of stray currents in the spa. Are the SS covers connected to metal that is presumably grounded? Or are they connected to plastic? If they are connected to metal, you might check to make sure the spa is properly grounded and you might consider attaching a sacrificial anode to that ground. You could check for electrical connectivity between the ground and metal components of the spa (no point in adding a sacrificial anode if there's no electrical connection). With pools, any metal in contact with the water is electrically connected together with a bonding wire, but I don't know if this is done in spas.

You are right that the ISIS system should have similar issues since it too uses salt.

I completely understand your desire to use the Trichlor system or the IntelliChlor because of the convenience of automated dosing. That's one reason why some people choose bromine, due to the slower dissolving tablets.

[Maastricht]

Chem Geek, thanks again for your help! I don't want to make it an ongoing discussion but I do have some more questions.

If I would go to a CYA level of 50PPM to make the chlorine less aggresive. I somewhere read that you advise a minimum FC level of 7,5% of the CYA level (so in this case about 4PPM) to prevent algae. Am I right? What would be then you advised maximum FC? I hope to get a bandwith feeling of what is good, so I am able to find the right setting on the Technichlor.

To come back on my experiments, I am not sure if temperature is a factor to consider but it's strange that the outcome is so much different.

The SS covers are clipped over plastic jets which make them look much nicer. So the SS covers are not connected to metal. However they are "connected" with the hot tub water which is connected to the Technichlor in which a current occurs between the plates which produces the chlorine out of the salt. Could this have an influence in you opinion?

All pump, of which the metal parts are in contact with the water are grounded to the switchboard. Our electrician tested the GFI? earth breaker a few times during the electrical installation of the spa. I am almost sure that this should be 100% due to the big risk getting electrocuted when using the spa if the water isn't properly grounded.

Just one more question, I read about studies which state that you always should shower after using a chlorinated swimmingpool or spa while human skin absorbs chlorine. On the long term this could have potential health effects. We have our bathroom upstairs and hot tub in our garden. When we use our hot tub, we now first shower to get in as clean as possible and should shower afterwards to get rid of the chlorine. Due to this 3 step approach it becomes a big ritual. I know you have read many studies to. What is your personal opinion about this topic?

Thanks again for helping us!

[Maastricht]

Hello Chem Geek,

I hope you are able to find a minute and would be willing to answer our questions above.

Thanks in advance!

[Maastricht]

Hello Chem Geek,

We hope you are willing to answer our questions above while we still don't feel very confident.

Thanks in advance for your help!

[jakenz]

Hi, I am pretty new to this so cant offer to much advice on the matter. However i can tell you that when we moved our spa out to an older shed, we immediaty began getting electric shocks from the spa. We traced this back to a faulty ground and once this was fixed we stopped getting shocked. So my thoughts on the matter are, if you are not getting shocked, your spa is properly grounded. Although that is a not a very good test i admit.

One thought i did have regarding your spa was the use of an automatic liquid chlorine feeder. This would allow you to get the benefits of the use of liquid chlorine, with the ability not have to worry about it when you go away.

[Maastricht]

Thanks Jakenz for your reply!

Personally I almost can't imagine that the root cause for the corrosion at our spa would lie in not proper grounding.

We also thought about a liquid feeder. The difficulty is that our spa is situated outdoor and according to my opinion the liquid chlorine could freeze. This was actually the main reason why we didn't choose for that option.

But thanks again for trying to help us!

[chem geek]

I'm sorry I missed this thread recently. Not sure why, but I did. Anyway, you don't generally need to worry about algae in a hot tub because it is covered pitch dark most of the time and is very hot the rest of the time. Algae need sunlight and moderately warm temperatures (not 100-104ºF or 38-40ºC). I would target around 2 ppm FC since most people start a soak with that amount so that they don't smell chlorine/monochloramine during their soak. If you want more disinfection to prevent person-to-person transmission of disease such as having unclean strangers over (!), you can target a higher number. Also note that the active chlorine level is higher for the same FC/CYA ratio at higher temperatures so the 7.5% rule doesn't apply and less is needed at spa temps (if we were concerned about algae, but we aren't).

As for the SS and it not being electrically connected, I think these SS covers are of poor quality. The combination of high spa temperatures, chlorine and salt cause faster corrosion, but these SS would probably corrode without the Technichlor salt levels -- it would just take longer. 38ºC would probably have corrosion be from 10 to 64 times faster than at 5ºC -- temperature makes a big difference. As for the salt, that might increase corrosion rates around 3x but shouldn't cause it to be runaway until higher salt levels, but it's possible with really crappy SS the chloride level at 2000 ppm is enough to interfere with reformation of the passivity layer. We know this happens with normal decent quality 316 (or at least 304) SS at around 6000 ppm or so, but perhaps with poor SS it can happen at a lower level.

As for skin and chlorine, chlorine does not get very far into skin because chlorine is quite reactive. It mostly reacts with the ammonia in your sweat in seconds to a minute to form monochloramine and oxidizes creatinine rather quickly as well. It oxidizes some chemicals in skin and becomes chloride while with other chemicals it forms Combined Chlorine (CC) as chlorinated organics. Some of these chlorinated organics can be absorbed through the skin and into the bloodstream, most notably the trihalomethanes (THMs). To reduce the amount of disinfection by-products, rinsing (a full shower isn't needed and soap isn't a good thing unless you can completely rinse all of it off) will reduce the amount of chemicals in your skin that can react with chlorine so yes, showering is helpful. As for showering afterwards, that's up to you but isn't as important since there won't be much chlorine left to react when you get out of the water. The amount of disinfection by-products is quite small, but rinsing before using the spa will help, but after not so much.

If your fill water has little bromide in it, then lifetime cancer risk is reduced because the chlorinated disinfection by-products are generally less harmful than the brominated ones. If you avoid drinking the spa water, then that significantly reduces intake of haloacetic acids (HAA) that have relatively little dermal absorption or volatility. The THMs are the ones that have more dermal absorption as well as some volatility, but without bromide there is only one THM, chloroform, and it does not cause cancer except that much, much higher cytotoxic levels. The haloacetonitriles (HAN) are volatile and the brominated ones have higher dermal absorption than the chlorinated ones so here again if you stick with chlorine you are better off compared to bromine. At levels seen in typical spas, risk factors are still very low -- where drinking 2 liters per day of spa water would have lifetime cancer risks in the 1 in 5000 range and you aren't obviously drinking that much and the amount from dermal and inhaled routes isn't that high either. Read the Environmental Health Criteria 216 "Disinfectants and Disinfectant By-Products" for a decent summary (I have many other links to papers on swimming pools, but they are a hodge-podge compared to this consolidated report on drinking water). The net result is that nothing is showing up in epidemiological studies in a big way (odds ratios are low and studies are inconsistent) though individual reports are cherry-picked by those with a financial interest in selling "alternatives".

Personally, I think it's more important for you to enjoy your spa. The difference between showering and not is mostly going to be in how much longer your water will last between water changes. For your health, it's helping to make a very small risk even smaller.

[Maastricht]

Hello ChemGeek,

Thanks for your very detailed answer, which gives much more information then I had hoped before!

This will also give my wife a much better feeling while you reffer always to epidemiological studies as a source. It's coincidence that my wife works for our local university and writes these kind of studies too. (but on different topics)

You are right it's now time to enjoy and throw all the corroded SS away. We will keep the Technichlor for now while this gives us very low water maintenance.

Greetings from The Netherlands and have a nice weekend!