It Can Happen to Anyone - Zero Chlorine, CYA-->Ammonia

[chem geek]

. Does anyone know if the ammonia test will get interference (accidentally measure) monochloramine? I don't know how the ammonia test works.
Richard

It depends on whether you are using a Nesslers reagent test (shades of yellow to brown and only works in fresh water since the mercury salts are precipitated by chlorides in the water) which tests total ammonia and ammonium ion (NH3 and NH4+)so it very possible will test monochloramine (not really sure since this is not normally an issue with testing aquaria) or a salicylate test (shades of yellow to green and works in fresh or salt) which only tests for ammonia itself (NH3) so it should not suffer any interference from monochloramine. The salicylate test is actually the preferred test to use because Nessler's reagent can give a false positive for ammonia in an aqauarium when it is actually in the form of an ammonium compound that is not toxic to fish (such as when 'ammonia killers' are added to the water.)

According to this link (see also this link, this link and this link), the salicylate test would appear to work by forming monochloramine and then measuring it so would definitely be interfered by monochloramine. It also appears that the salicylate test is for total ammonia and that is what it says on the test kit.

Ammonia + Chlorine ---> Monochloramine + Water
Monochloramine + Salicylate ---> 5-aminosalicylate + Hydrogen Ion + Chloride Ion
5-aminosalicylate --- (nitroprusside aka nitroferricyanide catalyst) ---> Indosalicylate

When I called to ask whether the ppm or mg/L units were ammonia nitrogen, the guy on the phone didn't understand and kept saying it measures total ammonia and then said the ammonia molecule, but most test kits (including a link above) say they measure in units of ammonia-nitrogen (i.e. 14 g/mole). It's not a huge deal since ammonia is 17 g/mole so not that different.

Richard

 

[piku]

Long after my ammonia reading was 0 I was still not getting an FC reading. In fact I gave up and started swimming in the pool because it was crystal clear and everything looked fine. I simply added what I felt was the appropriate amount of liquid chlorine daily. In a couple weeks after doing this I tested and noticed that I was finally holding an FC level. Luckily none of us got sick or infected with anything

That's really strange, especially since the water was clear. If there isn't measured ammonia and not substantial CC, then I'm at a loss for where the chlorine is going. It clearly gets consumed in some fashion and eventually holds. It's as if there is some other compound that acts like ammonia in terms of rapidly reacting with chlorine (but not all measuring as CC, so gets oxidized more completely), but doesn't get measured in the ammonia test. It could be one of the intermediates in the degradation pathway of CYA by bacteria (shown here).

CYA --> Biuret
Biuret --> Allophanate Ion

These intermediates would clearly react with chlorine as they contain nitrogenous groups (NH, NH₂) that often react with chlorine. Perhaps they do so in a way that breaks down quickly, similar to ammonia, and does not show up as very much Combined Chlorine (CC). This is in contrast to something like urea that seems to take far longer to break down -- many hours to a day or two (except at higher temperatures, such as in a spa).

If the above is what is happening, then if I had let my pool go longer before adding chlorine then the ammonia level would possibly have risen, but the algae problem would have gotten worse as well so that's not really something to do.

This is good information to know as the advice for clearing a pool in this way isn't just to look for ammonia, but to estimate the CYA loss to roughly figure out how much chlorine it might take. Adding chlorine every hour or so until it holds seems to be the prescription when this happens.

Richard

I wholeheartedly agree. Also it's worth adding tablespoons of chlorine to a bucket every couple hours until you hold an FC level to determine how much the pool will consume, that way you can determine the economics of a drain and fill versus throwing chlorine at the problem. In my case a complete drain and fill would have been far far far cheaper because water is really cheap for me.

 

[Guest]

According to this link (see also this link, this PDF file and this link), the salicylate test would appear to work by forming monochloramine and then measuring it so would definitely be interfered by monochloramine. It also appears that the salicylate test is for total ammonia and that is what it says on the test kit.
Thanks for the links. Several of the aquarium sites i frequent have this info backwards! (Not that surprising, the understanding of water testing and water chemistry is often way below that of the average member on this site, IMHO!)
When I called to ask whether the ppm or mg/L units were ammonia nitrogen, the guy on the phone didn't understand and kept saying it measures total ammonia and then said the ammonia molecule, but most test kits (including a link above) say they measure in units of ammonia-nitrogen (i.e. 14 g/mole). It's not a huge deal since ammonia is 17 g/mole so not that different.
Ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen is how the vast majority of aquarium testing kits express the results (not unlike how our borate test kits and strips are actually testing boric acid and expressing it as boron.)
Richard

 

[Donna's Poolboy]

I don't mean to thread jack, but this is pretty interesting and I'm starting to wonder if I have this same problem.
What are you guys using to test for ammonia levels? Is there a Taylor test and if so do you have the number?

 

[piku]

I don't mean to thread jack, but this is pretty interesting and I'm starting to wonder if I have this same problem.
What are you guys using to test for ammonia levels? Is there a Taylor test and if so do you have the number?

Nah, they are little aquarium test strips. Cheapest place to buy is walmart for like $10 a bottle.

 

[frustratedpoolmom]

Richard, have you witnessed this thread in the last day or so....can you check it out and chime in if you have any advice....

tf-100-test-kit-arrived-t10909.html

thanks,
Ann

 

[chem geek]

Ann,

I have followed it somewhat, but to be honest, I'm not sure I have any helpful advice. If test results are inconsistent, it's hard to know where to begin. I think y'all are doing the best you can. If the ammonia test result is correct and if the CC results are also correct, then it looks like there was a lot of ammonia in the pool (possibly from being let go and bacteria converting CYA into ammonia) and that adding chlorine is converting it to CC. With more chlorine, the CC can get oxidized away. I think that a bucket test, as was suggested, is in order to figure out the chlorine demand. If it's extraordinary, then a partial drain/refill might be another option to reduce the amount of needed chlorine.

Assuming there isn't any algae or "hidden" chemicals left to oxidize (as seemed to be in my case), then it takes around 8 times the ammonia measurement and about 0.6 times the CC measurement to get rid of these in terms of the cumulative FC needed. However, given the hidden intermediates that are possible, a bucket test would be wise. I think it's less likely for the intermediates to exist after a pool is let go since the bacteria keep on chuggin'. In my case, I caught things earlier before bacteria completed their conversion -- at least that's my best guess of my situation.

Richard

 

[frustratedpoolmom]

Thanks Richard, very helpful insight! (as usual.... )

 

[Donna's Poolboy]

Richard-
any idea what the break point of these organics is? I saw in an earlier post that you added 12.5 ppm of cl. At the time you had 0 cya.
I'm experiencing a similar situation to the one you've described in this thread and I'm wondering if normal shock levels aren't strong enough. I had a 40-50 ppm loss of cya over the winter and am experiencing massive cl consumption (15-20 ppm in 24 hours sometimes). However, overnight the drop is very small or zero. A 10ppm loss during the day is the norm for the last 3-4 days. My cya level is 40 (tested it 3 different times) and if things were "normal", a 2-3ppm drop during the day would be typical based on pool history (pool is in full sun from about noon til dusk). I used an aquarium test to check for amonia and it showed a trace of amonia (less than .5ppm) and today it's 0 ppm (sample stayed yellow). There were CC's in a couple tests early in this process but at low levels (1 ppm or less). For the last week cc's have been 0.

I started this process on 4/27 (10 days ago) and I've gone through 36 gallons of 12.5% cl. I've been vaccumming, brushing and backwashing daily and I seem to be getting closer but I don't think I'm out of the woods yet.
I've been trying to keep the free cl at around 20, but I'm wondering if I should crank it up (30? 40?) and hold it there until the decline slows to the 2-3ppm daily decline.
By the way, the water is 61 and crystal clear. You'd never know there was a problem!

Any thoughts?

Thanks,
Bill

 

[JasonLion]

The amount of chlorine lost to sunlight is a percentage of the starting FC level, not an absolute number. If you are maintaining a high FC level, your FC loss during the day will be far higher than if you have a lower FC level.

Secondly, the whole breakpoint story is misleading at best for outdoor pools. It isn't an FC level that you need to reach, rather it is a total amount of FC that you need to reach. The absolute FC level you can maintain is limited by your CYA level and the safety of the pool equipment.

If you are fighting ammonia in clear water and getting towards the end of the process, as indicated by very low amounts of FC lost overnight, you can switch to shocking only at night. That will save a great deal of chlorine, and only slow down the shocking process a little.

If your overnight FC loss is zero, and your CC level is zero and the water is clear then you are done shocking and there isn't any more ammonia.

 

[Donna's Poolboy]

In other words, my amonia problem has probably been solved about 3 cases of cl ago?

Okay...so when there is 0 FC loss overnight and 0 cc, I should just let the cl level drift back down to around 5 ppm (given my cya of 40). Correct?
Jason- is there a chart that shows the rate cl breaks down by sunlight? I remember reading that without cya, cl will be cut in half after 30 minutes of sunlight.

 

[chem geek]

Yes, unfortunately, you probably finished dealing with the problem days ago, whenever the overnight loss in FC was < 1 ppm.

There isn't a chart showing FC loss at different CYA levels. Roughly speaking, in strong intense long sunny days, at 30-40 ppm CYA one may lose around half of the FC in one day. At 50-60 ppm CYA, this may drop to around a loss of one-third. At 70-80 ppm CYA it may be one-fourth. However, these are very rough and your actual loss could be more or less depending on pool depth and other factors. So if you had an FC of around 20 ppm, then a loss of 10 ppm during the day sounds about right at your CYA level.

Richard

 

[piku]

Just opened today. Temp is 70, tons of soil in the pool from repeated yard overflowings into the pool. I figured I would be in for the same thing as last year but I checked the CYA and it registered 60. I dumped in 5 gal of 12.5% and the pool is nuclear So I'm good this year. My new Dolphin Pro is going nuts out there

 

[randytsuch]

My method for getting rid of CYA.

I have a solid safety cover on the pool, and since it's fiberglass, the PH doesn't change if I don't add chemicals.

So, I normally ignore the pool during the winter, when we don't use it. This year, I did shock the pool at the beginning of winter, maybe in Dec or so, with the intention of keeping it up over the winter. But, I didn't do anything until a couple of weeks ago, when I shocked it again, to bring it back up.

The point of this is that when I tested for CYA after the shock was done, it was 0. I filled that tube up to the top, and the black dot was crystal clear. CYA was maybe 40 when I last measured it, in the middle of last summer. CYA was also 0 at the beginning of last year, after an even more neglegent winter.

So, at least in my case, leaving the pool with basically 0 FC for a few months seems to get rid of CYA.

Randy

 

[JasonLion]

So, at least in my case, leaving the pool with basically 0 FC for a few months seems to get rid of CYA.

CYA does not reliably disappear under such conditions. Yes, you might lose all your CYA, but you might still have all of it at the end. It would be nice if there was an approach that worked every time.

 

[piku]

One would think if bacteria are responsible, you could put a healthy dose of CYA on a petri dish, expose it to some soil and the cultured bacteria would go to town. But I don't think it's that simple. It's probably only under certain ph conditions, temperatures and everything else.

 

[dschlic1]

The CYA eating bacteria seem to occur more frequently when a pool cover has been left on for long periods of time. There is some indication that the bacteria like low oxygen envirmments.

 

[chem geek]

I've read some sources that say it's anaerobic bacteria, but other sources such as this one that imply the conditions could be aerobic as well, at least from the abstract, but more careful reading of the full article looks like anaerobic conditions are the ones most favored by bacteria that break down cyanuric acid. Perhaps the abstract was wrong or they were referring to the general breakdown that could occur more quickly if enzymes were present independent of the bacteria.

 

[randytsuch]

So, at least in my case, leaving the pool with basically 0 FC for a few months seems to get rid of CYA.

CYA does not reliably disappear under such conditions. Yes, you might lose all your CYA, but you might still have all of it at the end. It would be nice if there was an approach that worked every time.

Hi Jason
I did not intend to present what I do as a method for lowering CYA, I just meant to give my example of CYA disappearance.

My conditions are somewhat unique, I have an opaque safety cover, and live in a climate where it never gets below freezing (maybe a few nights a year), and stop using the pool for about 6 months when if cools off. If you don't have those, you can't let your FC drop to 0 to months at a time.

The CYA eating bacteria seem to occur more frequently when a pool cover has been left on for long periods of time. There is some indication that the bacteria like low oxygen envirmments.

That matches my experience, maybe I am breeding this CYA eating bacteria over the winter?
Wonder if I could bottle the stuff? :-D

Randy

 

[Water_man]

Is it possible to lose all the CYA, but to have 0 CC and 0 ammonia upon
opening?