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

[chem geek]

As I reported in this post, I started up the solar system in my pool to get ready for the start of the swim season. Prior to this, the chlorine usage was very low at around 1 ppm FC or less per week. So last Saturday, 3/28, I added some Cyanuric Acid in the skimmer through an old T-shirt (so I could see if it was dissolving). The skimmer has a bypass so with a lot of CYA clogging it, most of the flow was in the bypass, but some went through the CYA as well. I checked the next day and the CYA was all gone so with this method and the pump set up higher (48 GPM) CYA seems to dissolve rather quickly. The CYA also had a measured increase of 20 ppm out of the 30 ppm I expected so it seemed to mostly dissolve. I also added one box of 20 Mule Team Borax to raise the pH (and to add some Borates, though I'm getting Boric Acid later to get it up to 50 ppm). So far, so good.

I had raised the FC level to 3-4 ppm on Saturday and figured it should be good for the week given the cooler temps and not opening up the opaque electric safety cover (i.e. no sunlight). Wrong! I opened up the cover yesterday (Saturday, 4/4) to find the water cloudy! I could still mostly see the main drain, but the water was most definitely cloudy, not just dull looking. I measured the FC and it was zero and the CC was 1.6 ppm. I had the beginnings of an algae bloom. Yikes! I immediately added some chlorinating liquid I had on hand, but knew it would not be enough. I also measured the CYA level and it was 0 (or at least a lot less than 20 ppm)!

So, today I went out and got some more chlorinating liquid as well as an ammonia test kit since the pool seemed to smell like ammonia and monochloramine when I added the chlorine to it. I tested it today and the FC was still zero but the CC was down to 0.8 ppm and the ammonia reading was around 2 ppm. If I assume that the warmer water got bacteria and algae to use up the chlorine faster, then perhaps the 3 ppm FC lasted 3-4 days which meant I had 3-4 days with zero chlorine. Apparently, that was long enough for bacteria to have a happy meal of CYA converting it to ammonia. The CC of 1.6 ppm is equivalent to 0.3 ppm ammonia and the 2 ppm ammonia I measured means a total of around 2.3 ppm ammonia. That corresponds to around 8 ppm CYA. I'll bet that a lot of the ammonia got eaten up by the algae which is what is making the water cloudy. I knew that water could turn cloudy from algae growth after a couple of days or so, but had no idea that the bacteria could grow and consume the CYA so quickly. Some people have reported fairly rapid conversion, but just a few days is pretty darn fast.

So, now I've got a lot more chorinating liquid in the pool and will retest the ammonia, FC and CC in an hour to see where I stand. Does anyone know if the ammonia test will get interference (accidentally measure) monochloramine? I don't know how the ammonia test works. With my separate CC measurement which is not interfered by ammonia, I can adjust for any interference in the ammonia test -- I just don't know if I need to do that. It's pretty approximate anyway since the ammonia test color comparison isn't precise (i.e. it's not a FAS-DPD, TA or CH kind of drop-test).

The lesson from this is simple. When starting up a pool and warming up the water, assume that the chlorine usage may go up considerably. Test frequently, which in my case (with the opaque pool cover) would have been at least a mid-week test so that the chlorine would have never gone to zero. During the swim season, I always test twice a week and add chlorine about twice a week which works fine for me and is quite predictable. I could just kick myself for not doing it during startup.

I'll keep you posted (in this thread) on my progress as I expect to clear this up quickly and will see if the CYA drop corresponds to the chlorine consumption from measured CC, ammonia and amount of added FC needed to eliminate the algae. I purchased some additional CYA, but will add that after I get this under control (might as well kill this stuff and oxidize chloramines quickly -- I don't care about nitrogen trichloride since it's an outdoor pool I can air out as needed).

Richard

 

[chem geek]

After about an hour, the ammonia now reads at between 0 and 0.25 ppm (not quite yellow; slight green tinge but not like the 0.25 ppm standard). So the amount of chlorine I added which was about 20 ppm FC oxidized around 2 ppm of ammonia as predicted. I've now added more chlorinating liquid and am going out to get some more since the cloudy algae will take more to get rid of and I want to get the FC to get up to shock level -- it's now still at zero with about 0.8 ppm CC.

I'll also start adding the CYA in the skimmer since my wife wants to start swimming tomorrow (we'll heat the pool with gas-assist overnight) -- not much time to get things into shape, but I'm pretty sure it'll be measuring FC and just be dull but clearing by tomorrow morning. We'll see...

 

[Guest]

. 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.)

 

[chem geek]

It looks like I've got the salicylate test since it shows shades of yellow to green. They even have two cards -- one for fresh water and one for salt water. I suspect the salt water card is for true ocean-style salt water. An SWG pool is probably not salty enough and would have colors closer to that on the fresh card -- at least my pool which has around 1200 ppm salt shows colors very much like the fresh water card.

So that's good that the test is better and not interfered by monochloramine. [EDIT] Wrong! It turns out that this test is also interfered by monochloramine and in fact it measures the sum of ammonia and monochloramine in ppm N units. The reason is that the first step in the test adds chlorine (using Dichlor) to convert ammonia to monochloramine and that it is monochloramine that is measured via the dye test. [END-EDIT]

The gallon of 10% chlorinating liquid (from Home Depot, since my normal pool store is closed on Sundays) now has me at miniscule chlorine of under 0.2 ppm (but definitely pink initially) with 1.2 ppm CC. So I'm past the ammonia stage and now at the "get rid of algae" stage and will add 2 gallons of 10% chlorine to get to around 10-15 ppm FC and will measure in an hour to see where things are at and add more chlorine as needed to keep the FC up. I'm also adding some CYA, but that will slowly increase between now and tomorrow.

Hope it clears up enough for my wife's swim tomorrow morning. I'm sure she'll notice the higher chlorine levels, but that'll be her choice and will still be far less powerful than her indoor pool swimming experience.

Richard

 

[chem geek]

So an interesting update. An hour after the 2 gallons of 10% chlorinating liquid, there was still <= 0.2 ppm FC and some CC. So I added another 2 gallons (this is roughly 12.5 ppm in my 16,000 gallon pool) and now I get an FC of 1.8 ppm and CC of 1.4 ppm. Looks like it's killing the algae and oxidizing it. With measurable FC I at least now know that the bacteria is killed so no more conversion of CYA to ammonia. I'm on my way, but jeez, this is gonna turn out to be an expensive mistake. I'm adding 2 more gallons now so that will be a total of 10 gallons or around 62.5 ppm FC cumulative. If I had 20-30 ppm CYA get converted to ammonia with some taken up with algae, then that would be around 67-100 ppm FC to get rid of it.

Now if we could only figure out how to intentionally add some soil bacteria into a pool with zero FC, have it convert the CYA to ammonia to lower the CYA level, not get so far as for full algae growth to begin, then hit it with chlorine to stop the process and clear out the ammonia, then we'd have a reliable way of reducing CYA without requiring dilution. Of course, the chlorine isn't free.

This experience just shows how much easier and less expensive it is to prevent problems by maintaining the FC level at all times. This is one argument for those that promote use of a regular algaecide or a phosphate remover (or metal ions, ignoring the staining issues) since it is insurance against such problems. It will be interesting to see what happens when I get the Borates up to 50 ppm -- to see if that can prevent this in the future (probably won't be till the end of the season before I do such an "experiment") though this is the first time this has happened to me -- not algae growth when chlorine got low, but the rapid bacteria conversion of CYA to ammonia.

Richard

 

[chem geek]

So the two gallons (12.5 ppm) and an hour later now results in 11 ppm FC so it's now a normal slower decline of about 12.5+1.8-11=3.3 ppm FC in an hour. The CYA has fully dissolved so I suspect that a large part of the slower oxidation of algae is the lower active chlorine concentration due to the CYA, but this is safer for equipment and especially for swimming tomorrow. Water is still cloudy, though appears to be clearing. I added another gallon to get to 17 ppm FC to somewhat speed up the process and to ensure there will still be some FC tomorrow morning. We'll see. [EDIT] I tested the water around midnight and it measured 15.5 ppm FC, so assuming the chlorinating liquid is at its correct strength, I'm still having a drop of chlorine consistent with slowly oxidizing probably dead algae. I'll see what it measures tomorrow morning to be sure. [END-EDIT]

Normally, it takes a few days to get completely clear when one has fairly cloudy water -- roughly the same amount of time it takes to get cloudy in the first place. I've got the pump running at higher speed for better filtration/circulation. After the pool gets fully clear, I'll test the CYA level to see if it's around the 30-40 ppm that I want.

Richard

 

[piku]

Yeah when this happened to me (my pool sat covered for a couple years), it took 100 gallons or more of 6% liquid to get it to hold an FC level 6 hours later. Don't be too quick to assume you have the problem conquered. I was able to get an FC level to register but it would disappear in several hours. This matched my bucket testing as well. Not a whole lot of fun really. I keep track of my expenses. It cost me $120 in chemicals to keep my pool going all summer and $400 to open

 

[chem geek]

I just measured the FC level and it's 14.0 ppm so that's a 1.5 ppm FC drop overnight. Not bad. The CC measured <= 0.5 ppm though there was clearly pink before adding the drop to turn it clear. The pool clarity is very significantly improved -- no longer cloudy and more of what I'd call dull. The floor drain is clearly visible so I do think I'm near the end and the pool will probably be in perfect shape by tomorrow. I'll just leave the FC high until then and will check the overnight drop from tonight to tomorrow morning.

My wife will be very happy. :-D The 14 ppm FC with probably around 30 ppm CYA or more is equivalent to 0.8 ppm FC with no CYA -- still less than the indoor pool she uses with 2 ppm FC and no CYA. Not a situation to keep permanent, but it's better than not swimming/exercising at all.

I hear you on the cost difference. My normal maintenance cost with the pool is around $15 per month. This mistake of mine took 11 gallons of 10% chlorinating liquid or around $36 (plus the additional CYA which was an additional amount I don't remember, maybe $20). Not horrible, but completely preventable.

Richard

 

[dschlic1]

It looks like you had the same problem I was having. Just finished a round with it last week. What ever it is, it can eat CYA very fast. In my case I have documented drops of 10 to 20 ppm in less than a week. Also be careful about assuming that you also have algae. This stuff can live in water that has normal or close to normal amounts of chlorine! The only way I have found to kill it is to use very high levels of chlorine (beyond normal shock levels) and keep it there for several days. Be sure that while shocking you circulate water through all of your piping. This stuff lives both in water and also on surfaces.

Once you decide to stop shocking, I recommend Poly 60 algaecide. It does seem to help reoccurances.

Now if we can only bottle this stuff to sell to people with too much CYA!

 

[chem geek]

Well, fortunately, it appears that in my case the high chlorine use was just getting rid of ammonia and possibly initial algae as well as killing the bacteria that likely caused me so much trouble (totally my fault for giving them such a nice no-chlorine home to grow in). Now that this is gone, the chlorine usage is relatively low. It dropped from 14.0 this morning to 12.0 tonight (CC < 0.5 ppm) with the pool being used by my wife for about an hour or so and the water heated to 88F. The water is now clear, even at night with the pool lights on. I'll keep monitoring chlorine usage and will remeasure all chemistry (especially CYA).

My Boric Acid arrived so I'll be using that to increase Borates, but my pH is low from the CYA addition so I'll get some Borax to raise it first.

Richard

 

[chem geek]

10.0 ppm FC this morning, so went from 12.0 to 10.0 or a 2.0 FC drop over about 36 hours with the pool not used (kept covered) during that time (we've had rain). That's higher than the normal <= 1.0 ppm FC per (24-hour) day, but at the higher FC level it's not too bad and would be < 1 ppm FC for a 12 hour overnight. Pool is now crystal clear. I'll replace my cartridge filters (4 cartridges) this weekend (they're 7 years old) and add the boric acid to get to 50 ppm Borates.

 

[lovingHDTV]

I'm glad it is happening to someone else other than just me. My pool looses all its CYA each off season as I don't keep the FC up. I'm in the process of bringing mine back up again maybe I should keep the FC up during the off season and see if that helps. I asked the pool store guy about it and he says "impossible".

So can I sell my pool water as a CYA reducer

 

[frustratedpoolmom]

So can I sell my pool water as a CYA reducer

Imagine the profits!!!!

 

[Guest]

It looks like you had the same problem I was having. Just finished a round with it last week. What ever it is, it can eat CYA very fast. In my case I have documented drops of 10 to 20 ppm in less than a week. Also be careful about assuming that you also have algae. This stuff can live in water that has normal or close to normal amounts of chlorine! The only way I have found to kill it is to use very high levels of chlorine (beyond normal shock levels) and keep it there for several days. Be sure that while shocking you circulate water through all of your piping. This stuff lives both in water and also on surfaces.

Once you decide to stop shocking, I recommend Poly 60 algaecide. It does seem to help reoccurances.

Now if we can only bottle this stuff to sell to people with too much CYA!

Now THIS is funny! :lol: :lol: :lol: (Private joke for Richard!)

 

[Need to Learn]

OK, I wouldn't normally wade into the Deep End, but I want to make sure I understand what occurred. I believe this scenario happend with my pool as I had a 30 to 40 PPM of CYA at the end of last season and then very low CYA when I tested it in March and I had not done any backwashing. I thought I had kept the FC up, but I did have some FC at one point.

It was my previous understanding that the only way the CYA will come down is by removing water by whatever means. So I did not understand how my CYA level could have come down and thought I was not testing correctly and when I was adding CYA it did not seem to be increasing the level as expected even after waiting a week. This thread seems to indicate certain pool conditions will consume CYA even if they are bad conditions.

I believe I have the situation stabilized now, but it would sure be nice to understand what caused the situation. I did have some fine dirt and leaves in the pool so perhaps when there was CC the CYA was converted to Ammonia? If there is a way to simplify the explanation of what occurred with Chemgeek's pool I would appreciate it!

 

[piku]

Yeah, in my case one or two times the yard floods and muddy water overflows through a crack in the coping into the pool during the winter. In the spring I always have a fine silt to clean out off the floor. So the suggestion that it's a soil bacteria of some sort makes sense to me.

 

[chem geek]

When you say you now have the situation stabilized, did you find that you needed to add a LOT of chlorine before it started to measure Free Chlorine (FC)? The symptoms and sequence for knowing that the situation of having bacteria convert CYA to ammonia has occurred are as follows:

1. Free Chlorine (FC) gets to zero at some point[/*:m:yyd144cl]
2. Bacteria grow and convert Cyanuric Acid (CYA) to ammonia[/*:m:yyd144cl]
3. One can measure >0 ammonia levels with an inexpensive test kit from a pet/fish/aquarium store[/*:m:yyd144cl]
4. There appears to be an insatiable demand for chlorine taking a LOT of added chlorine before FC begins to register[/*:m:yyd144cl]

So if the FC is zero and there is measured (> 0) ammonia, then the above situation is likely to have occurred. If you then add chlorine and after an hour or so the FC is zero and there is CC, then it's also likely for the situation to have occurred. The definitive test to know for sure is to test for ammonia right after opening the pool and before adding more chlorine. Normally, there should not be any ammonia in the pool water. If there is an unusual drop in CYA in addition to measuring ammonia, then it's pretty certain that the above situation has occurred (i.e. bacteria converted the CYA to ammonia).

I don't think that having dirt get into the pool and the CC go up is sufficient for this problem to occur. The FC needs to get to zero or very near zero since bacteria needs to be able to grow. Of course, CC represents chlorine that has been "used up" combining with something so odds are that when the CC went up, the FC went down. The key is to know whether the FC get to near zero. (NOTE: dschlic1 described a situation where things happened even with a normal chlorine level, but that could be algae growth instead of bacteria; I suppose it is possible for some type of algae to "eat" CYA and convert it to ammonia the same way that some bacteria do, but it's the first case of this I've heard.)

The easiest way to avoid this situation is to always maintain chlorine in the pool and never let the FC get to zero, not even for a day.

Richard

 

[chem geek]

I thought I'd sum up a chronology of what I measured and added to the pool.

Mon, 3/23: water temp 57F (solar heating started)
Sat, 3/28: crystal clear water; FC 3-4 ppm, CYA added (for about 30 ppm); water temp 74F
Sun, 3/29: crystal clear water; CYA measured 20 ppm
FC went to zero at some point; bacteria apparently converted CYA to ammonia; algae grew turning water cloudy
Sat, 4/4: cloudy water; FC 0; CC 1.6; CYA << 20 (maybe 0); added about 6 ppm FC
Sun, 4/5 1:15 PM: FC 0; CC 0.8; ammonia 2; added 12.5 ppm FC
Sun, 4/5 2:45 PM: FC 0; CC 0.8; ammonia 0-0.25; added 12.5 ppm FC; added 20-30 ppm CYA
Sun, 4/5 3:45 PM: FC 0-0.2; CC 1.2; added 12.5 ppm FC
Sun, 4/5 5:00 PM: FC 0-0.2; some CC; added 12.5 ppm FC
Sun, 4/5 7:00 PM: FC 1.8; CC 1.4; added 12.5 ppm FC
Sun, 4/5 8:00 PM: FC 11; added 6.25 ppm FC; water temp 76F (gas heating started)
Sun, 4/5 11:50 PM: FC 15.5
Mon, 4/6 8:00 AM: dull (not cloudy) water; FC 14.0; water temp 84F
Mon, 4/6 10:00 PM: clear water; FC 12.0; CC < 0.5; water temp 86F (gas heating stopped)
Wed, 4/8 11:00 AM: crystal clear water; FC 10.0; CC < 0.5 (10 ml sample)
Thu, 4/9 9:00 AM: crystal clear water; FC 9.8; CC < 0.2 (25 ml sample); water temp 75F
[EDIT]
Fri, 4/10 6:00 PM: crystal clear water; FC 8.6; CC < 0.2; water temp 81F (gas heating started in AM); CYA about 22
will add more CYA, some Borax to get pH a little up, and then the Boric Acid for the Borates
Sun, 4/12 4:00 PM: crystal clear water; FC 5.8; CC < 0.2; water temp 88F
Wed, 4/15 11:45 AM: FC 3.4; added chlorine (about 3 ppm FC)
[END-EDIT]

It took at least 56 ppm FC to get to a point where the chlorine was holding reasonably. That corresponds roughly to 23 ppm CYA degraded to ammonia (or to ammonia taken up by algae). What is interesting is the rapid consumption of chlorine on Sunday even after the ammonia measurement had dropped to near zero. This could have been chlorine oxidizing the algae (note the continued presence of CC), but I didn't think that normally happened so quickly. Perhaps it does initially, oxidizing "easy" chemicals in algae and then the process slows down after that. Or perhaps the cloudiness was from lots of bacteria and not from algae (it never got to the point of turning green, so hard to tell). Or maybe the ammonia test was wrong when it measured near zero ammonia (after reading 2 and having chlorine added). [EDIT] Or the chlorine demand can be from partially oxidized CYA that doesn't show up as either ammonia nor as CYA. [END-EDIT].

Richard

 

[piku]

I thought I'd sum up a chronology of what I measured and added to the pool.

Mon, 3/23: water temp 57F (solar heating started)
Sat, 3/28: crystal clear water; FC 3-4 ppm, CYA added (for about 30 ppm); water temp 74F
Sun, 3/29: crystal clear water; CYA measured 20 ppm
FC went to zero at some point; bacteria apparently converted CYA to ammonia; algae grew turning water cloudy
Sat, 4/4: cloudy water; FC 0; CC 1.6; CYA << 20 (maybe 0); added about 6 ppm FC
Sun, 4/5 1:15 PM: FC 0; CC 0.8; ammonia 2; added 12.5 ppm FC
Sun, 4/5 2:45 PM: FC 0; CC 0.8; ammonia 0-0.25; added 12.5 ppm FC; added 20-30 ppm CYA
Sun, 4/5 3:45 PM: FC 0-0.2; CC 1.2; added 12.5 ppm FC
Sun, 4/5 5:00 PM: FC 0-0.2; some CC; added 12.5 ppm FC
Sun, 4/5 7:00 PM: FC 1.8; CC 1.4; added 12.5 ppm FC
Sun, 4/5 8:00 PM: FC 11; added 6.25 ppm FC; water temp 76F (gas heating started)
Sun, 4/5 11:50 PM: FC 15.5
Mon, 4/6 8:00 AM: dull (not cloudy) water; FC 14.0; water temp 84F
Mon, 4/6 10:00 PM: clear water; FC 12.0; CC < 0.5; water temp 86F (gas heating stopped)
Wed, 4/8 11:00 AM: crystal clear water; FC 10.0; CC < 0.5 (10 ml sample)
Thu, 4/9 9:00 AM: crystal clear water; FC 9.8; CC < 0.2 (25 ml sample); water temp 75F

It took at least 56 ppm FC to get to a point where the chlorine was holding reasonably. That corresponds roughly to 23 ppm CYA degraded to ammonia (or to ammonia taken up by algae). What is interesting is the rapid consumption of chlorine on Sunday even after the ammonia measurement had dropped to near zero. This could have been chlorine oxidizing the algae (note the continued presence of CC), but I didn't think that normally happened so quickly. Perhaps it does initially, oxidizing "easy" chemicals in algae and then the process slows down after that. Or perhaps the cloudiness was from lots of bacteria and not from algae (it never got to the point of turning green, so hard to tell). Or maybe the ammonia test was wrong when it measured near zero ammonia (after reading 2 and having chlorine added).

Richard

Richard,

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

 

[chem geek]

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