CYA at 150 -- How Did I Get There and Now What?

[Yukon]

I have a new Hotspring Pulse (380 gal, covered, 24/7 circulation pump, 100F) that was installed end of Sept, so just a couple months old. I put both an ozonator (Freshwater III) and a metal ion stick (Nature 2) in it from the start, hoping that would allow me to minimize chemical additions. For a while, water was crystal clear, then one day, got very cloudy. I knocked it back to clear with dichlor, but since then, I seem to be cycling between bacteria bursts and crystal clear. As a result, my CYA levels (according to the Aquacheck 7 test strips I use) have climbed to 150.

Since the beginning, I have used MPS (about 1.5 tbsp after each use or every 2 days) during the week, and dichlor (1 tbsp) once each weekend. There are usually just 2 or 3 people in there for 30 minutes every couple days or so, so I think the bather load is not a huge problem. With either the MPS or the dichlor, all traces of the stuff disappear within 8-12 hours, no matter what. I have been assuming that the ozonator is breaking it down quickly, but in any case, it is very difficult to maintain any level of either chemical. I would literally have to add it twice a day to keep any sort of concentration in the spa. All this would be great if the ozonator also knocked down the bacteria blooms as quickly, but apparently they can multiply faster than the ozone and metal ion system can kill them (or those system don't work, which I'm sure many will claim.)

I use the N2 test strips to check for MPS levels, and I test for Cl- and pH/TA using a Pool Master reagent kit. If I put in 1 tbsp of dichlor, it shows 2.0 - 3.0 ppm on the reagent test kit and around 5.0 with the test strips. The reagent kit only reads as high as 5.0, but I've never seen it that dark. No matter what, it will be back down to near zero within half a day or so. Other parameters seem good - pH is stable around 7.6 and TA has been between 50 and 100ish. Calcium Hardness is 250 on the strips.

So I feel like I'm using very little dichlor, though when fighting these cloudy events, I have put another tablespoon or so in during mid-week to get the water clear again. However, the strips are telling me that CYA is past 100 and more like 150, after just two months after filling.

Can someone provide some guidance on this?

1) Is my chemical regimen just too conservative and I should be adding Cl- and/or MPS more often?
2) Is my ozonator helping or hindering me in my attempt to minimize chemical additions?
3) Are my CYA measurements accurate?
4) How did I get to 150 on CYA so quickly?
5) Do I now need to drain fully or partially to get the CYA levels down? I'm concerned that my Cl- levels are not being as effective, hence the cloudy cycles.
6) If I start over, what's the best way to proceed?

I know you guys talk about using liquid bleach, but the Watkins manual is emphatic that it should not be used and will damage the acrylic, etc., etc. I would prefer to go that route, but would like some guidance from those who have done this.

Any help greatly appreciated!

 

[zethacat]

Welcome to TFP!

You can use pool math to determine how much CYA is added per ounce of dichlor (scroll to bottom). It only takes 15 Oz of dichlor to add 150ppm CYA to 380 gallons of water. The only way to reduce CYA is to replace water.

 

[pwrstrk]

Welcome to TFP !
Ditch the test strips. They are not going to give you accurate test results and the folks here on the forum won't trust the results from them to base our advice on.
Here are the Test Kits we recommend using for their accuracy. The TF100 is the best value. You can get it at TFTestkits.net. I use it along with many other members.
Bleach won't hurt anything in your tub.?

 

[chem geek]

Welcome to TFP!

3 people for 30 minutes every 2 days is 5.25 person-hours per week. With no ozonator (yes you have one, but I'll deal with that later) this would require around 5.25*3.5 = 18 teaspoons of Dichlor or 5.25*3.5 = 18 fluid ounces of 8.25% bleach or 5.25*7 = 37 teaspoons of non-chlorine shock (43% MPS) to handle the bather load. With an ozonator, the required amount might be half though it really depends on the strength of the ozonator (and how long it runs).

You have added 1.5 tbsp so 4.5 teaspoons of MPS every 2 days or roughly 16 teaspoons per week and 1 tbsp so 3 teaspoons of Dichlor every week. With no ozonator, this would be enough to handle (4.5/7)*(7/2) + (3/3.5) = 3.1 person-hours of soaking per week. So if your ozonator is functioning properly then this should roughly be enough to handle the bather load, but since your MPS shows getting used up and not maintaining any residual it would seem that either your ozonator is not working or it is not strong enough to handle your bather load given your MPS and Dichlor dosing. You need to use enough MPS so that you still measure a small residual by the time you start your next soak.

The ozonator does react with chlorine but it does NOT react with MPS. So you aren't adding enough MPS after each soak. It does seem that your ozonator may not be functioning properly. If you end up needing to use roughly the amounts of oxidizer I indicated with no ozonator, then this would be another confirmation that your ozonator isn't working.

As for the CYA level, for every 10 ppm Free Chlorine (FC) from Dichlor, it also increases Cyanuric Acid (CYA) by 9 ppm. So your regular 1 tbsp per week in 380 gallons would be 5.5 ppm FC and 5 ppm CYA. This would be around 21 ppm CYA per month, but your shocking with Dichlor to get rid of problems is the likely main source of the high CYA after several months since "another tablespoon or so midweek" would be another 5 ppm CYA per tablespoon. Of course, test strips can be very poor, especially at measuring CYA and may be reading falsely high.

You should get an accurate test kit. The FAS-DPD chlorine test is more accurately read than the DPD test it sounds like you may be using (unless you are using an OTO test that is even worse). See the Pool School article Test Kits Compared and do yourself a favor and get a proper test kit (either the TFTestkits TF-100 or the Taylor K-2006).

If you get a better test kit and it measures the CYA as not being as high, then you can work with the water you have. However, since you have been going through bouts of cloudiness that may be bacterial blooms (especially if you feel spa surfaces being slimy; if not, then it's more likely unoxidized organics), I'd suggest using Ahh-Some just before your next water change since that will clear out any greases or biofilms in piping. You should see if you can figure out if your ozonator is working. I'm not sure if any of the available reasonably priced ozone tests don't get interference from either MPS or chlorine, but you could test when your ozonator is presumably running and when MPS and chlorine are zero. This Spa Ozone detection test and this Del Ozone™ test appear to work by measuring ozone in the ozone output tubing so are testing gas and not ozone in the water so should not get interference. Ths SenSafe® Ozone Check in water test could be used to check a sample of water going into the spa, but might get interference from MPS or chlorine.

The main reason that spa manufacturers such as Watkins in the HotSprings Limelight Owner's Manual say not to use bleach (note that they do NOT say why) is mostly because if you use ONLY bleach with no CYA in the water then the chlorine is too strong and can degrade hot tub covers faster as well as be harsh on other equipment components (doubtful that it would affect acrylic which is pretty chemically resistant - note in this link that a 1/3rd concentration bleach solution, so roughly 20,000 ppm FC solution, is used to clean acrylic spa surfaces!). There are many hot tub users on who use the Dichlor-then-bleach method so are using bleach after building up CYA in the water and there have been no reports of any problems (on multiple forums, not just this one) though one must be more diligent about the pH after switching to bleach which is why using 50 ppm Borates is recommended for additional pH buffering. Once bleach is in the water that already has CYA, it is chemically IDENTICAL to using Dichlor except that the CYA won't continue to build up over time. In your case, if you use Nature² then you'd be using mostly MPS anyway and only using Dichlor once a week or so if you need to do so to keep the water clear (with a properly functioning ozonator, that usually isn't necessary).

 

[Yukon]

Thanks, all, for the rapid and informative responses!

I will definitely upgrade my test kit and will spend some time reviewing the references you provided.

The ozonator (Freshwater III) was installed by the Watkins people after the tub was installed. It runs 24/7, with the circulation pump, and appears to be producing small bubbles from the pipe. Does the fact that Cl- goes to zero so quickly perhaps indicate that the ozonator is working? I guess I'll have to look into testing it, but I was going on the assumption that a brand new system from the manufacturer should be working fine. The guy that installed it said it appeared to be working well, but who knows? Certainly, I was beginning to conclude that "this ozonator is doing nothing!", so maybe you are onto something with the unit being faulty. Maybe I can get the Hotsprings people to check it....?

Bumping up MPS is, I guess, an easy (and the most palatable) fix. Based on your numbers, and assuming for the moment that the ozonator is simply not chewing through organics the way I would like, I could go to 1.75 tbsp every single day for a while, and see if that breaks the cloudiness cycle. What do you think?

Once I get a reliable way to measure CYA, I can decide about replacing the water. But based on my current water chemistry, and making the assumption that CYA must be well above 50 in any case, can I just begin using liquid bleach now without doing anything else? Or do I need to add some borates first?

Thanks again!

 

[chem geek]

With an ozonator running 24/7 then yes the chlorine would get used up quickly probably 50% every 4-6 hours so not much left after 24 hours. Normally one does not run the ozonator that long. Ozone will damage your spa cover, spa pillows, and other equipment faster if it's running that long. However, ozone should not affect the MPS level and you said that also dropped. Note however that bather load will use up chlorine and MPS very quickly so you can't assume the ozonator is working just because chlorine is depleted unless you don't have any bather load and there's nothing leftover to oxidize.

Yes, you can up the MPS but just keep in mind that it's not as good an oxidizer as chlorine in some ways so you may need to keep using chlorine on occasion as well, but just weekly as you have been doing.

And yes, you can use bleach in place of Dichlor now since in any event you likely have at least 50 ppm or so CYA. As for borates, if you use bleach you have to watch that your pH doesn't rise too much. If your Total Alkalinity (TA) is much higher than 50 ppm you may find the pH rising and that can cause scaling especially since your CH seems high. Normally you only have your CH at 150 ppm to prevent foaming. Note that test strips generally test for Total Hardness, not Calcium Hardness, so they include Magnesium as well -- another reason why test strips are pretty useless.

 

[Yukon]

I'm not sure how to make the ozonator run any less than 24/7, since it just runs with the circulation pump. It did not appear to have any timer system on it when he installed it. I'm not sure what to make of the ozonator: on the one hand, it seems not to be able to keep the water clean, even with the amount of MPS and dichlor I'm putting in it (not to mention the metal ion system); on the other hand, running it 24/7 seems to be overkill and could even be too much ozone! I guess I really do need to test it and see if it is working. I'm leaning toward the in-water test strips you recommended, as I can be pretty certain MPS and Cl- is close to zero when I do the test.

Bather load for the past 8 days is zero. During that time, we went from clear to cloudy and back to absolutely crystal clear (yesterday and today). Yesterday, I put 2 tbsp of MPS in there, just to see how long it lasted. 24 hours later it reads between zero and low on the N2 test strips. Again, nobody has been in the tub for 8 days.

I have a Taylor K-2006 kit on order. I will try putting MPS into the tub every day and see how that goes, as well as shifting to liquid chlorine once a week. My TA is currently 80 but not sure about Ca hardness, as I only have what the test strips show me (around 250). I will continue to monitor pH levels closely to ensure the bleach does not push that too far.

I have been keeping track of everything for the past 2 weeks in an Excel file, but not sure how to attach it. Can send it to you if that would be helpful.

 

[chem geek]

Are you sure the cloudiness just isn't something temporary like getting air into the jets? Some spas run the jets a short time every so often (at least once a day -- usually a few times a day) to ensure disinfected water gets into the jets so that they don't develop biofilms. It's quite strange for the water to turn cloudy and not just stay that way since whatever caused that problem one would think would continue to persist.

 

[Yukon]

No, it's definitely not air. It starts out mildly hazy/cloudy/milky and gets worse over hours/days, even after I start treating it. The jets only run when I turn them on. The difference between what it is now (crystal clear) and hazy is very easy to notice.

For example, the last cycle went like this: Water was clear before use. Five bathers for 30-45 minutes (an unusual event) at night (no use of the hot tub subsequent to this event). 1 tbsp dichlor upon exit. Next morning, water looks very slightly hazy. Two days later, 1.5 tbsp MPS - water still mostly clear, but a bit hazy. Two days later, 1 tbsp MPS in morning, water looks slightly more hazy. MPS is mostly gone in 3 hours and water looks cloudier. 1 tbsp dichlor that afternoon and water is very cloudy. Next morning, water looks slightly cloudy, Cl- is gone. 1 more tbsp dichlor in the morning and 1.5 oz of enzyme (Leisure Time) in the evening. Next day, water is a bit more clear, but not perfect. 2 tbsp MPS. Next day, water is crystal clear, and continues crystal clear to today (the following day).

Maybe I'm imagining things, but I feel like I'm getting just behind the curve of an exponential bacterial bloom. Eventually, the chlorine and MPS chews it (and/or its food) up and it dies off. There is no residual "slimy surface" as you mentioned before. It just seems to go back to perfectly clear until the next cloudy event. I think this is the fourth time it has happened. Previously, it has produced foam after treatment when the jets are running, but I skim it all off until the water is clear again. But in each case, I definitely get after it with my chemical arsenal, so no, it does not really have a chance to persist. Then, when I go back to my conservative chemical regimen, it pops up again.

Like I said, I'm taking detailed notes, so maybe a pattern will emerge. Perhaps if I am more aggressive as soon as I notice the first hint of cloudiness, I can beat this cycle. But I guess I am disappointed that the "alternative" systems (ozone, metal ion) are not able to "hold their own".

 

[chem geek]

Well if you find out that the ozonator isn't working then maybe all that is happening is that you aren't using enough oxidizer initially after the bather load so it instead is forming intermediate products that make the water cloudy and eventually when you add enough these intermediates get more fully oxidized or filtered out. If you had a working ozonator truly running 24/7, it should oxidize all that bather waste within a day. I look forward to your report on what you find out about your ozone level from the ozonator.

 

[Yukon]

You may be right - two of us went in last night for 30 min, and I put 1.75 tbsp of MPS in the filter compartment as we exited. 12 hours later, the MPS test strips show "OK" (0, Low, OK, High) and the water remains crystal clear.

I will report back when I have better data on the water parameters and performance of the ozone system.

Thanks again for the help!

 

[Yukon]

I now have a Taylor K-2006 test kit, which is super nice. Water parameters are as follows: CH = 200, TA = 80, pH = 7.5 This reads as perfectly balanced water. At present, MPS and Chlorine are at zero, but I will add bleach tonight. Water has been crystal clear for the past 6 days. Bather load has been 2 people for 30 minutes for 2 of those 6 nights.

I have not yet purchased any test kit for the O3, but I think it is working. Even if nobody uses the tub and the water is clear, FC goes to zero very quickly whereas MPS residuals remain over the same period of time. The implication is that the ozonator is burning up the chlorine components, even when there is little to no bather waste. I know...best to test it, which I will do eventually.

I'm putting more MPS (1.75 tbsp) after each use, and will put even more if there are more than 2 bathers, which occasionally happens. Looking at my notes, the last cloudy event came right after we had 5 people in there, so maybe the ozone and metal ion systems just could not keep up with that level of bather waste, and I was simply not using enough MPS or chlorine to knock it down.

Now, my problem is that the Taylor kit confirms my concern about the CYA level. I had to use a 50/50 sample/tap water mix, and the reading is around 130. Bloody dichlor... I am now using bleach, but the damage has been done. Do I need to dump this (perfectly balanced) water and start over?

 

[zethacat]

Yes I believe you do

 

[Yukon]

Is the problem with CYA that the levels of acid themselves are harmful to bathers, or is it more a matter of the CYA reducing the sanitizing power of the chlorine?

 

[jblizzle]

With high CYA, you must maintain higher FC levels for the water to be sanitary.

If the FC is above 10ppm, then your pH test is no longer valid

 

[Yukon]

I think I'm going to just let it go another month, then. I have the metal ion system, the ozonator, the MPS additions, and the (CYA limited) chlorine, so I think I'm ok, despite those high CYA levels. I put 3.5+ oz of bleach into the tub the other evening after leaving it unused for several days, which (mathematically) took my tub to 6 or 7 ppm. By morning the FC reading was like 0.2, so I'm pretty convinced that the ozonator is working. I think my error all along was not putting enough MPS (and dichlor) following large numbers of bathers.

 

[chem geek]

OK that sounds like a plan. Be sure and let us know if using more oxidizer after your soak solved the problem consistently.

 

[Yukon]

Yes, I will update the thread over time. So far, it appears to be working well. Not just the oxidizer, but the additional chlorine via bleach. Two factors now contribute to me being less reticent to bump the chlorine levels up: 1) the stuff just does not last - I can put in 4 oz of 12.5% bleach in my 380g tub and it will be down to 0.2 ppm in the morning, so by the time I go into the tub again, there is not much chlorine residual. Since I have the metal ion and ozone systems going 24/7, I am not too concerned about bathing with somewhat low FC levels. 2) now that I'm using bleach rather than dichlor, I am no longer building up my CYA levels. I know my CYA is still too high, but I was resistant to put too much dichlor when I knew it was just building up CYA in the water. Now, I can chlorinate with impunity!

Richard, is there any way to know what is causing the hazy/milky/cloudy effect when it happens? I have read elsewhere that it's not necessarily the bloom of the bacterial colony that shows up as cloudiness, but the evolution of the cloudy effect in my tub certainly seems to fit the pattern of an exponential growth cycle, with chemical additions causing a complete reset. And for sure, when I do get back in front of it with plenty of chlorine, the water is so obviously, noticeably crystal clear.

Also, if I use both MPS and bleach upon exit, how far apart do I need to space these additions to the water? Can I put one in right after the other?

Thanks!

 

[chem geek]

It makes no sense for the bacteria to bloom when there is any disinfectant in the water or with the ozonator running 24/7. Even if the MPS was getting depleted, the silver ions from Nature² should prevent uncontrolled bacterial growth even though they don't kill quickly enough to prevent person-to-person transmission of disease. Also the ozonator should prevent uncontrolled growth when it is on (which in your case is 24/7) since turnover time isn't very long and the bloom is in the bulk water that should be getting circulated and not just on surfaces where the ozonator may not have any effect (unless there is residual ozone in the water). Finally, bacterial blooms are usually associated with slimy surfaces since they prefer a surface upon which to reproduce -- they do not as readily divide in the middle of the water so need to be on particulate matter (e.g. dead skin cells) or a spa surface, especially to form biofilm. It's algae that tend to cloud the water more readily but they take a lot longer to reproduce (3-8 hours per generation compared to 15-60 minutes for bacteria). I really think the bloom is something chemical, possibly something intermediate in the oxidation of the bather waste. However, I would think that with continued circulation that the ozone would eventually handle it. When it blooms, does it not go away with continued circulation or did you not wait to see and just added chlorine to get rid of it?

You can put in MPS and chlorine one right after the other since they do not react with each other.

 

[Yukon]

This is *exactly* what has been puzzling me, and what led me to post the thread in the first place. It just seems as though there should not be a chance for bacteria to really get going, yet I do see this cloudy event every now and again. You are right, once I see the water taking on that cloudy look, I hit it with chlorine, MPS, and enzyme. It can take a couple days to get back to fully clear, but once I start treating it, it gets no worse. The first time it happened, I didn't react as quickly, and the water did get very cloudy.

There are no 'slimy surfaces' that I can see, unless they are in the pipes, and this system was built custom and has only been installed for less than three months. Turnover on the circulation pump is 240 gallons per hour, so the entire supply of water should go through the filter every 90 minutes or so. Subsequent to the cloudy events, the water does tend to develop foam when aerated, which it normally does not.

So, under the following circumstances, what could this be? If nobody has been in the spa for several days, the water has been treated with bleach and MPS following the last soak and some residuals remained the next day, the N2 system and ozonator are working 24/7, and after a few days, the water starts to become cloudy and gets cloudier each day it is untreated with additional MPS or bleach. In this case, can we assume bacterial growth? Algae seems unlikely, as the spa is covered, and it would seem there is no remaining bather waste. I guess I could experiment and see what happens if I add no chlorine once the cloudiness begins (though I'd rather not do that...).