Help Needed For Indoor Hot Tub Please

[Loumart]

Hi all

I'm really pleased I found this forum as my tub came with NO instructions about the water chemistry & care!

I installed the hot tub in my conservatory in October and have been using the aqua finesse water care system as it sounded great at the time (maybe too good!). I followed the instructions to the letter but the water would sometimes go cloudy and smell To clear this I would shock it with chlorine and it works but it seems to me that the aqua finesse system is crap! My main reasoning for this is that I ended up in hospital just before christmas with hot tub lung!!! My chest has been bad again recently so I wish to change the way I look after my water - I'm hoping you great people can help ;-D as I have next to no idea but I've been learning from this forum.

My tub only holds 900-1000 litres of water. I live in a soft water area of England and as I said, the hot tub is located in my conservatory (3 glass walls and a opal plastic roof). The conservatory is south facing so gets the sun.

This is what I've learnt from the forum but I still need help please:

1. Fill the tub with clean water

2. Adjust the total alkalinity with baking soda to acheive 70ppm (starts at near 0!)

3. adjust the PH of the water to 7.4 (starts at or below 6.8)

4. shock the spa with MPS so its present to break down organics and urea before chlorine & so reduces/eliminates Combined chlorine (no need to super chlorinate the spa to shock)

4. use Dichlor to sanitise the tub until a level of 15 to 20ppm of CYA exist then switch to bleach to chlorinate

5. keep the chlorine levels at 3 to 4ppm at all times

6. Shock the pool with MPS once a week to keep the reserve up in the water

I'm not sure how much MPS I need to use in the above or even if the above is correct! Any advice would be greatly appreciated - does it look right to you?

I'm wanting the spa to smell as little as possible as it indoors and will make my home smell. Is it safe to use the spa indoors without ventilation or should I open the windows when I'm using it?

I've heard that chlorine can be a problem with indoor spas - why is this? I read (on this forum) that chlorine can produce carcenogenics (obviously I dont want this) and TMH's - what are TMH's please?

How often do I need to add extra chlorine or is this just trial and error until you get it right? What is the maximum safe chlorine level while using the tub?

Sorry about all of the questions but I want to play it safe as my little girls use the tub as well as myself.

Please help

Thank you in advance

Martin

[Loumart]

Someone please help

[Private Shrink]

Someone please help

I wish that I could promise that this would help, but I can at least offer my experience. I live in Maryland, USA and my hot tub (about 220 gallons, don't know how that translates to liters but it's small) is in my sunroom which is essentially all glass. We had the room build with the hot tub in mind, so many glass windows open, we have two ceiling fans to assure circulation, and we had a powerful exhaust fan installed in the ceiling right above the tub, which is set back in an alcove a bit from the glass areaand, therefore, there was a good place to install the fan. So, we were prepared to get rid of excess humidity and who knows what else. But we also have been using BaquaSpa since we got the tub in August. As I've learned on this site, there are three approved methods for water maintenance...chlorine based, bromine based, and baguanide based, the one I'm using being the third. Every method has it's good and bad points, but I wanted no smell, no green hair, etc., just clean clear water. So far, that's exactly what we got and with minimal work...once a week I check readings and put a few things in. We use well water, and I think that this helps us because it lacks some of the stuff that treated water has. My less than expert advice is to see if you can get a baguanide based system, totally clear out your tub, and start with this. On the other hand, a local dealer warned me that some people get "BaquaSpa cough," and you said that your lungs were already affected. I would also see if there's anyway to exhaust some of the air or at least circulate it, as that was one of our life saving ideas. Good luck and I hope you get some other helpful responses.

[chem geek]

Martin,

I'm sorry to take so long to respond, but with all the spam that is hitting this forum your post got "lost" so I didn't see it until now. I will try and answer your questions.

As for how much MPS to use, you should go by the recommendations on the bottle scaled down to your spa size. Pool non-chlorine shock is usually 1 pound per 10,000 gallons which would be around 0.8 ounces per 500 gallons (or 0.4 ounces in your 250 gallons -- that's about 11 grams). However, spa non-chlorine shock has a recommendation of 2-4 ounces per 500 gallons so that would be 1-2 ounces (28 - 57 grams) in your 250 gallon spa. This would be added about once a week unless your spa isn't heavily used in which case it could be once every two weeks. You can also buy monopersulfate test strips that will show you if you are maintaining a residual in your spa so that might be a better guide (or the Taylor K-2006 test kit can be enhanced with the K-2041 which can selectively measure MPS and remove its interference from the FC/TC test).

The sun exposure sounds like it is going through glass so that will cut down the UV that breaks down chlorine so I wouldn't worry too much about that. Besides, your initial use of Dichlor will protect the chlorine from breakdown from sunlight (slowing such breakdown; it doesn't stop it).

To keep the smell to a minimum, I suggest that you keep the spa covered when not in use, then remove the cover and open a window for brief ventilation before you jump in. You don't have to keep the window open once you are in unless you find too much buildup of odor -- you'll have to determine that for yourself. Your initial use of Dichlor with its CYA should keep disinfecting chlorine concentrations low enough to keep the odor down to minimal levels.

THMs are trihalomethanes that are one class of several chlorinated organic compounds some of which are carcinogenic. You shouldn't worry about that in your spa for two reasons. One is that your initial use of Dichlor means that your spa will contain Cyanuric Acid (CYA) which will make the effective disinfecting chlorine (HOCl) concentrations lower and lower concentration means a lower rate of production of disinfection by-products (DPBs) including THMs. Second, is that your use of non-chlorine shock (MPS) will oxidize organics before chlorine has a chance to combine with them and that virtually eliminates the problem of DPBs and THMs. In other words, you will be quite safe.

You will have to find out through experience how frequently you have to add chlorine. Using a spa cover will help significantly to keep the chlorine in the spa when not in use. You should keep a minimum of 4 ppm FC in your spa (assuming the 20 ppm CYA level from the initial Dichlor usage which introduces 0.9 ppm of CYA for every 1 ppm FC that is added) and so long as you initially use Dichlor to get your CYA level up to 20 ppm, then you can have your FC level up to even 10 ppm and be technically equivalent to a spa that has 0.75 ppm FC with no CYA. So I would say keeping your FC in the range of 4-8 ppm is fine. You may find that you need to add more chlorine after every use of the spa since the aeration of jets and your sweating in the spa will tend to use up or outgas the chlorine faster than at any other time. On the other hand, your using non-chlorine shock cuts down chlorine usage.

Don't forget that after your initial use of Dichlor for some number of days or weeks (until you've added about 22 ppm of FC to get 20 ppm of CYA), you switch to using unscented bleach (e.g. Regular unscented Clorox). If you splash-out and refill with water at all, you might want to check the CYA level every few weeks to ensure it is still at approximately 20 ppm (it is hard to measure that since most kits measure to 30 ppm so the black dot won't completely disappear in the test at 20 ppm). I suspect that you'll only have to check the CYA perhaps once a month if at all since you will completely replace your water typically every 3 months.

I hope that answers your questions. And be sure to report back with how it works out for you, what your chlorine usage is, if it smells, etc. We all learn from actual experiences.

P.S.

I'm really sorry about your hot tub lung. You can read more about it at this link. Note that they say that "added chlorine loses most of its disinfectant properties at temperatures above 84 F", but that isn't exactly true. At higher temperatures the chlorine will tend to evaporate out of the water so it reduces in concentration and THAT makes it less effective, but in your spa the use of CYA helps slow down this process and besides, you are going to stay on top of the chlorine levels in your spa. You'll see that the CDC recommends 2-5 ppm FC, but they don't talk about CYA. I suspect that most cases of hot tub lung and hot tub itch are from people using exclusively Dichlor in their hot tub and when the CYA gets to high levels, the chlorine disinfection ability is lowered to the point where the bacteria are able to grow. In your case, Aqua Finesse appears to be an enzyme and not chlorine (or bromine or biguanide) so it probably wasn't disinfecting very much at all -- probably enough for easy-to-kill bacteria like E.coli, but not enough for the bacteria that cause hot tub itch and hot tub lung.

[EDIT] See this link for an update. Note that the use of Aqua Finesse without a sanitizer is not recommended and appears to be the main problem that led LouMart to get hot tub lung. Aqua Finesse may inhibit biofilms, but it does not kill bacteria quickly enough to prevent their growth. [END-EDIT]

[Loumart]

Thanks to both of you for replying to my post

Private Shrink - I've read about the baguanide based system and it sounded perfect to me at first as it has no smell and only needs weekly maintenance. The downside appears to be that it can leave a brown goo and it only last a few years before bacteria become immune to it so I'm not sure about this system at the moment - I think I'll try chlorine with MPS first. As for the ventilation - I'm now playing it safe and opening all the windows and doors while the tub is in use. I use a large dehumidifier to get rid of the water vapour and it works great Again, many thanks for your input

Chem Geek - I'm pleased you replied as you really seem to know your stuff! I have a few more questions if thats ok mate. Is all non chlorine shock based on MPS - I've been looking on ebay but cant find MPS but there are lots of different non-chlorine shocks.

Does MPS alter the reading of the FC test on normal test strips or is it just the Taylor kit?

Do you have any idea where I can purchase the Taylor-2006 kit in the UK please?

I've just refilled the spa and used dichlor to bring the FC upto 6ppm for its first dose - the water has been sitting for 36 hours like that and the chlorine level hasnt dropped yet (But I havent used it either). There is quite a smell of chlorine at the moment but its not too bad.

I dont have any MPS at the moment - can I add this at a later date or does it have to be put in before the chlorine on a fresh fill? Will I need to shock my water every week without MPS?

Thanks again for everything and I'll keep you posted as to how things pan out

Cheers

Martin

[chem geek]

Martin,

Let me try and answer your questions below:

Is all non chlorine shock based on MPS - I've been looking on ebay but cant find MPS but there are lots of different non-chlorine shocks.

Most non-chlorine shock is MPS -- just look on the bottle for something that says "potassium monopersulfate" or "potassium peroxymonosulfate". There are some other non-chlorine shocks that are not the same such as ones that say "percarbonate" or "perborate".

Does MPS alter the reading of the FC test on normal test strips or is it just the Taylor kit?

That's a good question and I don't know for certain. It most certainly interferes with the DPD and FAS-DPD Combined Chlorine (CC) test. It does not interfere with the Free Chlorine (FC) test so likely does not interfere with the FC test on normal test strips. The main inteference with the CC test is only right after a treatment so waiting 8 hours before doing the CC test is usually sufficient and as I mentioned there is a Taylor K-2041 MPS interference remover which also lets you measure if you have an MPS residual.

Do you have any idea where I can purchase the Taylor-2006 kit in the UK please?

I called Taylor and you can order from their website http://www.taylortechnologies.com but that would involve international shipping charges and would take longer. They do not sell to pool stores in the U.K. though they are looking into that. That's really too bad because I did a quick look at pool stores in the U.K. online and could only find test strips and not complete tests (or FAS-DPD chlorine drop tests). I didn't look very long so maybe I missed something, but I'm sorry to not find out anything more for you about that.

[EDIT] It looks like you can get some decent tests at this link which is mostly PlainTest products. They use tablets instead of liquid, but they do have a separate test for CYA and Calcium as well as the standard Chlorine/pH/TA test and they have a combination kit SP315C. Surprisingly, they don't seem to have a test for Combined Chlorine. This site has a good Lamotte test kit and that includes Combined Chlorine. Lamotte competes with Taylor in the U.S. and they are both good companies with good kits, so maybe that is your best bet except you'll need a separate CYA test so maybe the Lamotte PM 41 combined with the Plaintest SP620 is your best bet. [END-EDIT]

I've just refilled the spa and used dichlor to bring the FC upto 6ppm for its first dose - the water has been sitting for 36 hours like that and the chlorine level hasnt dropped yet (But I havent used it either). There is quite a smell of chlorine at the moment but its not too bad.

Initially, because the CYA is lower, there will be more outgassing of chlorine and hence more smell. This will decline as you raise the CYA closer to 20 ppm.

I dont have any MPS at the moment - can I add this at a later date or does it have to be put in before the chlorine on a fresh fill? Will I need to shock my water every week without MPS?

You can add it later, but it is designed to be used before organics get into the spa so is used on a weekly basis. It is not a disaster if you don't use it right away. Some people use chlorine alone and do not use MPS, but it's harder to keep the CC down if the spa isn't exposed to sunlight and since you are also more concerned about health issues, the MPS is useful for eliminating the disinfection by-products.

If you keep your FC above 4 ppm at all times, then you probably will not need to shock your water since your water will be "continually shocking" due to the FC residual. If you find that your Combined Chlorine (CC) rises, especially above 0.5 ppm, then you may need to shock with chlorine (bleach, not Dichlor). It really depends on your bather load (how many in your hot tub for how long -- and how much chlorine is in the tub and if it stays above 4 ppm at all times).

[Loumart]

Your a star chem geek mate.

The second site you gave do sell a full test kit including a CYA test The kit is for an outdoor pool but I think its the same but with the addition of the CYA test. Would you mind having a look and letting me know what you think - http://www.swimmingpoolchemicals.co.uk/pro...products_id=120

Also, I think they sell the MPS I've been looking for its called potassium mono peroxy sulphate

Thanks again for everything

Martin

[chem geek]

Yes, that kit looks good. It's essentially like the Taylor K-2005 test. The main difference between this and the K-2006 is that the chlorine test is a DPD colorimetric test (i.e. you compare the color to a guide) instead of a more accurate FAS-DPD drop-based test. For your purposes, the DPD test should be fine. It's just harder to discern small amounts of chlorine, specifically combined chlorine, since that's the only chlorine level that will be small in quantity (since you will always be keeping FC at least at 4 ppm).

Yes, the MPS name you quoted is the right stuff -- funny how these names can get flipped around -- must be a British thing

[Loumart]

Hi again mate - I'm nearly there - lol

I take it that the stuff which rids the MPS misreading in the TC test will also give me the MPS concentration with an extra test + a bit of maths.

MPS = Total Chlorine (before mps-out) - total chlorine (after mps-out) is this correct or is there another way to measure MPS?

Also, is the taylor's version of MPS-OUT (Deox I think its called) compatible with the lamotte kit (I think it should be) as I cant find MPS-OUT to buy over the net for some reason! Also, if its not too much trouble could you please tell me the order code (product number) of the taylor chemical to prevent MPS interaction with the FC test.

I really appreciate your help and I was stumped before finding this forum!

Thanks again mate

Best regards

Martin

[chem geek]

My answers to your questions below:

I take it that the stuff which rids the MPS misreading in the TC test will also give me the MPS concentration with an extra test + a bit of maths.

MPS = Total Chlorine (before mps-out) - total chlorine (after mps-out) is this correct or is there another way to measure MPS?

Yup, you've got it. Those are the instructions exactly and should come with the MPS deox from Taylor. You can read the Taylor instructions at this link.

Also, is the taylor's version of MPS-OUT (Deox I think its called) compatible with the lamotte kit (I think it should be) as I cant find MPS-OUT to buy over the net for some reason! Also, if its not too much trouble could you please tell me the order code (product number) of the taylor chemical to prevent MPS interaction with the FC test.

Yes, the Taylor MPS Deox is Taylor kit K-2041 for the small size (0.75 fluid ounce) bottle and K-2042 for the large size (2 fluid ounce) bottle. Since the K-2042 isn't much more expensive, I'd just get the larger bottle since shipping will be a big expense. You may find it at this link. You'll note that these instructions are for FAS-DPD in the first section and then later on they have instructions for DPD which is more like your Lamotte test except Lamotte uses tablets while Taylor uses liquid. The key is to add the Taylor R-0867 reagent right after color develops in the chlorine test but before you then measure the FC and especially before you add the reagent that lets you test for CC.

As to whether this will work with the Lamotte kit, that's something you'll have to ask Taylor (you can post them a question on their website). They are really good about answering questions. However, they might not know the answer to this since the Lamotte test isn't made by them, but I suspect that it will work since the DPD test is similar for both -- Lamotte uses a tablet, Taylor uses liquid (for DPD; powder for FAS-DPD).

[chem geek]

Martin,

I did some more research on the chlorine smell when using chlorine in hot tubs and have some more suggestions for you. It seems that if you take your cover off and ventilate for 5 minutes and then get in the hot tub, there is less smell, and you should add more chlorine AFTER you get out of your hot tub (as opposed to before you get in). Also, as I said in a previous post, until you've used Dichlor a few times to get the CYA up to 20 ppm, you will be outgassing more chlorine so the smell will be more noticeable. I'll be interested in finding out how the smell is after about a week or so when you switch to using just bleach. It will also be interesting to see if using the non-chlorine shock helps because maybe you are smelling chloramine and not chlorine (with non-chlorine shock in the water, you shouldn't form any chloramine).

[Loumart]

Hi again mate

Yeh, I would defo prefer to add the chlorine when I get out of the tub but is this safe if the chlorine levels are low when I get in? The reason I ask is that if the chloring level is at say 4ppm when I get in then its usually only about 1ppm when I get out!

I added to much bleach one time before I got in (well over 5ppm - this is all my strips measure to!). After been in the water for only 1 minute of so I got really itchy all over and this lasted for many hours when I got out of the tub. This isnt something I'd like to repeat.

You are also correct about leaving the cover off for 5 mins before using the tub as this is when the smell is strongest and I was wondering if it was chlorination too - time will tell when I switch to MPS shortly

Oh, I've been in touch with Taylor and they cant tell me if their de-ox is compatible with the Lamotte kit. They told me their could be prodlems

I'll keep in touch as promised and let you know what happens but I need to find the MPS-out for the Lamotte test system

Best regards

Martin

[chem geek]

In a PM to me you mentioned how you were using crushed up Trichlor instead of Dichlor for adding chlorine and CYA. Since Trichlor has more chlorine per CYA than Dichlor, you really don't have as much CYA as you think. The amount of Trichlor needed to add 1 ppm FC adds 0.6 ppm CYA while the amount of Dichlor needed to add 1 ppm FC adds 0.9 ppm CYA. So your lower CYA levels mean that the amount of disinfecting chlorine is higher so that means more smell, more usage through outgassing, more possibility for itching (if FC levels are high and CYA isn't high), etc. Using Dichlor will get your CYA level up faster and hopefully reduce these side effects or you can try crushing up and dissolving Trichlor more frequently (just remember that it is very acidic so check your pH after you've added it and mixed it in your spa).

The other information in the PM that was interesting was the amount of bleach you needed to add to maintain chlorine levels. It was much higher than expected and though it might be that the inexpensive bleach brand is very low in sodium hypochlorite concentration, it may also be that you have a lot of chlorine demand in your spa. Once you get your CYA level up, it will be easier to determine what's going on since the CYA will help reduce the loss of chlorine from outgassing. So if the FC level still isn't maintained well, then you've got something in your spa using it up rapidly. It is normal for the FC to drop during your use of the spa since the cover is off, the water is hot, and you are running the jets (so aerating). The higher CYA will slow down this chlorine loss. If you are only at, say, 6 ppm CYA, then getting to 20 ppm CYA (with an FC of 4 ppm) will cut down the rate of loss (and smell) by over a factor of 5.

Remember that when you "switch to MPS" you aren't really switching from anything. After you've added enough Dichlor or Trichlor to get your CYA up to 20 ppm, you will still be adding bleach to keep the FC at around 4 ppm. The MPS might cut down the consumption of chlorine, but it won't replace it unless you are also using bleach currently to do shocking. Shocking with chlorine, by its very nature, will have a lot of smell associated with it since the FC levels will be higher. So that's one big benefit of using MPS instead of shocking with chlorine. Even though the MPS will interfere with the CC test, it should be OK to use even now since after 8 hours you won't have any interference at all with the FC test and possibly only a small amount of interference with the CC test (showing a "residual" level of MPS). If I were you, given the problems you've mentioned, I would get the CYA level up (try to dissolve the Trichlor you can crush or if it just won't dissolve fast enough try Dichlor which is better for spas anyway since it isn't so acidic) and immediately start using MPS on a weekly basis. You will likely get your good test kit soon and the MPS-out intereference remover within a few weeks.

[Loumart]

As you now know my CYA level is at about 23ppm so this should be ok. I'm now adding bleach when I get up on a morning and another dose at about 7pm or when I've used the tub which is usually about the sam time. The needed dose is about 225ml each time as the FC test usually only shows 1ppm and I like to increase it to 4ppm as you suggested. The smell isnt to bad but when new bleach is added the smell does get stronger for an hour or two.

I think I may start using the MPS in the next few days. I have a few questions about using the lamotte test kit if the MPS doesnt interfere after 8 hours (or at least not much). Would it be possible to do the following:

EVERY DAY DO THIS:

1. Every morning test the FC level. Add required bleach then test the level again to make sure its correct.

2. Do the same in the evening or after using the tub

EVERY WEEK DO THIS:

1. Test the FC and add bleach as normal

2. Test for CC as the residule MPS should be low and shouldnt interfere to much with the test

3. Test PH

3. Add MPS

This way I may not need the MPS-OUT will I? Please let me know if I've missed anything as this is going to be my 'testing routine'

Thanks again

Martin

[chem geek]

That sounds OK though you might find some residual CC in your test that is actually measured residual of MPS. The MPS-OUT would be more definitive, but you could just see that the CC level doesn't grow. If it does, then if you skipped using the MPS for a week and the CC stayed about the same, then it's probably the MPS residual. If the CC grows without adding MPS, then that tells you it's "real" CC and not MPS. So not having MPS-OUT is a little dicey, but you can try it. Odds are, you won't have any real CC when using MPS regularly.

You probably don't have to do the verification test after adding your bleach every day. If it's from the same bottle, it's probably the same concentration. You could do the verification less frequently, even once a week.

I'm still amazed at how much volume of bleach you need to add to raise the FC level. That is awfully weak bleach you have! At some point, you might try using (or borrowing from someone) a better brand to see if it measures stronger. You're mostly paying for water and packaging so I suspect that in the long run, using a stronger bleach will actually save you money even if it "seems" more expensive per bottle.

The rapid decline in chlorine concentration is one of the reasons people prefer using bromine in their spa since they can use a bromine tablet feeder and the bromine also doesn't outgas quite as rapidly. But some people are more skin sensitive to bromine.

Now that you have your Lamotte test, try seeing if the CYA test shows anything. That would be a good verification that you have enough CYA in your spa.

[Loumart]

Cheers mate - I've purchased some MPS test strips for the moment until I find the proper MPS-OUT for the lamotte kit.

Also, I've found a site which sells 14% sodium hypochlorite in the UK The price is only £36.33 delivered and I've worked out its only going to cost me about 8p per day in my 950 liter spa. Its as cheap as my supermarket bleach but I know it wont have the additives so peace of mind

If anyone is interested here is the link http://www.safe-servers.co.uk/~chemicals/a..._Bromine_7.html

Cheers

Martin

[chem geek]

Martin,

The only thing to keep in mind with concentrated chlorinating liquid is that it does not last as long. It's half-life is dependent on temperature and concentration. This table gives you some idea of this chlorine half-life. At reasonable temperatures, it should have a half-life of over 3 months so that's pretty good. Essentially, you should store the chlorine in a very cool place and away from any sunlight. Note also that the cap must be on securely and if there is any leakage then the chlorine vapors can corrode metal that is nearby so be sure to put it in a ventilated area. I haven't found any problem with my 12.5% chlorine that I use, but some people who have stored it in a garage have noted rusty bicycles, etc.

If they sell a less concentrated version (12% or 10% or even 6%) at a lower price, that would be a better bet for you since you don't need it really concentrated and it will last longer.

Another word of caution. The concentrated chlorine bleaches out everything a lot faster than regular bleach, so make sure you aren't wearing any clothes that you care about and be careful not to splash any -- wear glasses or goggles (goggles are better, but I wear glassses anyway and am careful in pouring).

[Loumart]

Wow, I didnt realise bleach degraded so quickly! I think the bleach should have a half life of around 5 months in our climate (UK) going off the table but thats still quite bad to me as the bleach is going to last me approx 1.5 years! Am I correct in thinking this means it will only be 7% bleach after 5 months and 3.5% after 10 months?

If I add water to the bleach to reduce its strength it should last longer right? I'm thinking half bleach and half water to make the bleach 7% to start. Maybe this wont work but I thought I'd ask as it seems more stable as lower concentrations.

Also, is sodium chlorate toxic - I know its a strong oxidiser but is it safe is spa water. The reason I ask is that bleach produces this as it decomposes.

Thanks a million chem geek mate

Best regards

Martin

[chem geek]

Your calculations about the half-life are not quite right because the lower concentration doesn't degrade as quickly. The first part is correct that from the table at 15% (which is close to your 14%) at 75F the half-life is 148 days or about 5 months at which point it will be about 7% and the rate of degradation drops during the 5 months, but that's taken into account in the table. The 7% at 75F is in between the 5% and 10% so we'll split the difference and assume a half-life of 752 days or about 25 months.

So you are correct that if you add water to the bleach you receive to reduce its strength then it will last longer. In fact, that is what most pool stores do. They often receive 14-15% strength and dilute it to 12.5% or 10% or whatever they end up selling. If you dilute the bleach you receive with an equal quantity of distilled water (and I would only use distilled water for that purpose since any metals or other impurities in the water can quickly degrade chlorine), then you will increase the life of the bleach significantly so that effectively you could say that it is in decent quality for a year. Since it's not that expensive, I don't think you'd want to dilute even more and try and keep the stuff for more than a year -- probably better to just buy some more every year to play it safe.

Chlorine degrades to form several things including oxygen, but the chlorate isn't good stuff to add to your spa, but it's not horrible either. It is used in commercial herbicides. It is toxic in larger concentrations such as injesting over 214 mg per kilogram of body weight, but that's far more than you'd ever injest by swallowing water in a pool or spa. I know that the website link I gave describes problems with oxygen and chlorate, but that's more an issue for using the chlorine to sanitize drinking water. Nevertheless, since it's easy to avoid or to reduce by simple dilution of the chlorine you receive, then that's a good idea.

[Loumart]

Good news on the 'watering down' of the bleach Would tap water be really bad to use as I'm not sure where to get 25 liters of distiiled water for cheap As I've said, I live in a soft water area and the calcium level is below 60 on the lamotte kit (this is the lowest it measures to).

Oh, the CYA level in my tub was about 24ppm but my PH was 8.2, alkilinity 160 and calcium hardness below 60 as I've said I need to purchase a few more chemicals.

I look forward to hearing what you think about my tap water before I purchase the 14% bleach

Thanks again

Martin

[chem geek]

If you have one of those reports from your municipal utility that purifies your water and it shows no (or barely detectable) levels of metals or contaminants, then you *might* be OK. Odds are, your water company is probably adding either chlorine or monochloramine to your water (you should be able to tell with your test kit -- chlorine will show up as FC while monochloramine will show up as CC). Anyway, I think you're taking a risk if you use your tap water, but the worst thing that would happen would be that you find that your diluted chlorine loses its FC faster than you expected and you should be able to tell that (by seeing how much liquid volume it takes to add an amount of FC to your spa) so if that's the case you can then "know" that the tap water wasn't a good idea and do something else at that point. It's not a disaster (though could cost you some money).

HOWEVER, did you say 25 liters of distilled water? If the strength of your chlorine averaged around 6% after dilution (it starts at 7%, but then goes down over time), then this should be about 60 ml for your 950 liter spa to add 4 ppm FC. If you did that every day that works out to about 22 liters of DILUTED chlorine or about 10 or so liters of concentrated 14% chlorine. In other words, you shouldn't need to buy more than about 10 liters of the concentrated chlorine for a 1 year supply, and that assumes the 4 ppm FC per day usage which might change. You're also making a bold commitment to chlorine so I hope you are OK with the smell you've mentioned.

Last, but not least, how and where were you going to be storing all of this chlorine? I suppose you could buy additional jugs, but I'm a bit concerned about safe storage. You want to keep the stuff sealed reasonably well and in a well-ventilated area and away from metal, etc. One thing you can do is to keep some chlorine test strips around near where you store the chlorine. If they measure or show chlorine (perhaps after being moistened), then that's a problem and indicates some leakage. You'll also want to check on your stored chlorine to make sure none of the bottles is bloated -- that would indicate generation of oxygen (most likely) and would indicate impurities and breakdown of the chlorine.

[Loumart]

I wish I could buy a smaller amount but it comes in 28KG tub only which I assume is 25 liters. I've tested my tap water for FC & CC and found nothing at all which I was supprised at - I though all tap water had a little chlorine in.

I also tested the cheap bleach I have from the supermarket and it is only 1.5% lol - no wonder it took so much bleach to raise the FC in my tub. 95ml of this bleach is only raising my FC by 1.5%

I was thinking of storing the strong bleach in my shed but now I'm not sure as I have a lot of 'toys' in there I'd like to keep. I'm now thinking about keeping it either in the old coal house or outside in the shade - will it be ok outside?

I'm thinking about making an automatic feeder for the bleach using a syringe a couple of valves and a stepper motor. The who thing will be controlled by a microcontroller. The main problem with this could be the bleaches action on rubber seals - does it atteck rubber and if so is there a 'safe' concentration?

Once again, thanks for all of your help and the great info - I now feel quite confident about caring for my tub water.

Cheers

Martin

[chem geek]

Well at least now we know why you were using so much bleach.

The (half-diluted) bleach will be OK outside so long as it is in shade. You definitely do not want direct sunlight to hit it even if it's in an opaque tub since higher temperature makes the chlorine break down more rapidly. So, outside in shade should be good and you already indicated that your temperatures are not likely to get very warm.

I know that the rubber in my wife's swimsuits degrade after just one winter season of use in an indoor pool (which probably does not have CYA in it, so the disinfecting chlorine level is high), but there might be some types of rubber that are more resistant. I honestly don't know.

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