Ready to fill it with dirt and start a garden

[chem geek]

That's very interesting. As I describe in this post, the first degradation step of CYA by bacteria converts it to Biuret. If for some reason the Chinese had biruet in addition to CYA in their mix, then chlorine would oxidize the biruet so would lead to an increase in chlorine demand and maybe biruet shows up as CYA in the CYA test so as it got oxidized the apparent CYA level would drop. Another possibility, and one that is even more likely, is that they have urea in the CYA product since urea very likely shows up as CYA in the melamine test (see this post for more info), though urea takes longer to break down unless there is sunlight and chlorine (i.e. in indoor pools it doesn't break down very quickly).

In the Interference in Melamine-based Determination of Cyanuric Acid Concentration article, they note that you can reduce the interference by adding one drop of sodium hypochlorite (i.e. chlorinating liquid or bleach) to the CYA test sample AFTER you've added the melamine reagent and formed a precipitate. It would probably be a good idea to take a reading before adding the chlorine and then take another afterwards. The article speculates about the source of the interference as being ammelides or ammelines or chloramines, but I suspect it's more likely to be urea especially in your case where no CC was seen.

Note that the article also says that superchlorination (what we call shocking) seemed to be the consistent solution for correcting the incorrect cyanuric acid readings. This is essentially what you have been doing with your pool.

Do you know what brand of CYA you have been using?

 

[izjay]

That's very interesting. As I describe in this post, the first degradation step of CYA by bacteria converts it to Biuret. If for some reason the Chinese had biruet in addition to CYA in their mix, then chlorine would oxidize the biruet so would lead to an increase in chlorine demand and maybe biruet shows up as CYA in the CYA test so as it got oxidized the apparent CYA level would drop. Another possibility, and one that is even more likely, is that they have urea in the CYA product since urea very likely shows up as CYA in the melamine test (see this post for more info), though urea takes longer to break down unless there is sunlight and chlorine (i.e. in indoor pools it doesn't break down very quickly).

In the Interference in Melamine-based Determination of Cyanuric Acid Concentration article, they note that you can reduce the interference by adding one drop of sodium hypochlorite (i.e. chlorinating liquid or bleach) to the CYA test sample AFTER you've added the melamine reagent and formed a precipitate. It would probably be a good idea to take a reading before adding the chlorine and then take another afterwards. The article speculates about the source of the interference as being ammelides or ammelines or chloramines, but I suspect it's more likely to be urea especially in your case where no CC was seen.

Note that the article also says that superchlorination (what we call shocking) seemed to be the consistent solution for correcting the incorrect cyanuric acid readings. This is essentially what you have been doing with your pool.

Do you know what brand of CYA you have been using?

I have been using two different brands of CYA. One is from Pinch a Penny (local chain) and one is from a non-chain place down the street. The place down the street packages their CYA in zip lock bags and prints labels that they stick on the bag. I assume they buy it in bulk. I wonder where you can buy CYA that is definitely not from China. By the way, my pool finally seems to have leveled off. Hopefully it will stay that way.

 

[chem geek]

The GLB brand from Advantis (now part of Arch Chemicals that is part of Lonza) is reasonably priced compared to other name brands, but I don't know if they source from China. I do know that they test their source chemcials so it's less likely for them to have impurities. That's generally true for other name brands as well. Mostly, though, we haven't heard of this problem before so it's may be limited to the off-brand sources you've been using.

 

[izjay]

That's very interesting. As I describe in this post, the first degradation step of CYA by bacteria converts it to Biuret. If for some reason the Chinese had biruet in addition to CYA in their mix, then chlorine would oxidize the biruet so would lead to an increase in chlorine demand and maybe biruet shows up as CYA in the CYA test so as it got oxidized the apparent CYA level would drop. Another possibility, and one that is even more likely, is that they have urea in the CYA product since urea very likely shows up as CYA in the melamine test (see this post for more info), though urea takes longer to break down unless there is sunlight and chlorine (i.e. in indoor pools it doesn't break down very quickly).

In the Interference in Melamine-based Determination of Cyanuric Acid Concentration article, they note that you can reduce the interference by adding one drop of sodium hypochlorite (i.e. chlorinating liquid or bleach) to the CYA test sample AFTER you've added the melamine reagent and formed a precipitate. It would probably be a good idea to take a reading before adding the chlorine and then take another afterwards. The article speculates about the source of the interference as being ammelides or ammelines or chloramines, but I suspect it's more likely to be urea especially in your case where no CC was seen.

Note that the article also says that superchlorination (what we call shocking) seemed to be the consistent solution for correcting the incorrect cyanuric acid readings. This is essentially what you have been doing with your pool.

Do you know what brand of CYA you have been using?

I finally got around to the test you suggested. I did it three ways. The first time, I did the CYA test as normal. I got a 40 which is up 10 from the last time I tested it. I have not added any stabilizer to the pool. The next test, I used a q-tip to add chlorine to my water sample before I added the regent. This time the test came out as if there was not any CYA (the vile stayed clear until the top). The last time, I added the reagent to the test water like normal and shook it up like normal. Then, I added chlorine with a q-tip. Again, the vile stayed clear until the top. So, maybe my high chlorine levels were interfering with the test. My FC is still at 16, so I will wait to add CYA until my FC level gets back down to normal. My FC is dropping at a more of a normal rate now. Hopefully this is a good sign.

 

[linen]

Chem geek probably needs to confirm this, but I think you may have hit it.

I think your conclusion is wrong though.

If the drop of chlorine (after mixing in the melamine) did not influence the test, then it would have indicated the test was normal and at least the interferes that could have been caught by adding the drop of chlorine, were not in the sample.

However, in your test (when you added the drop after mixing in the melamine), you no longer indicated cya. From this I would conclude that you have bad (contaminated) cya.

I would repeat the test again. This time use something other than the qtip to add the drop. A clean eye dropper or a clean glass or plastic rod would be better.

Then do the cya test normally. Get a consistent reading a few times...you can do this by pouring the solution back into the mixing bottle...repeatedly if necessary. Then add the drop of chlorine again to the already tested solution and retest until you get a consistent result.

If you still see ~40 ppm cya then after the drop see something much closer to zero (filing tube to top) then I think you will have confirmed you have a interfferent, and we should start thinking about some different cya.

Again, someone else (chem geek or others) should probably comment. I wouldn't wait to do the repeat test though...I am very anxious to hear your results.

 

[izjay]

Chem geek probably needs to confirm this, but I think you may have hit it.

I think your conclusion is wrong though.

If the drop of chlorine (after mixing in the melamine) did not influence the test, then it would have indicated the test was normal and at least the interferes that could have been caught by adding the drop of chlorine, were not in the sample.

However, in your test (when you added the drop after mixing in the melamine), you no longer indicated cya. From this I would conclude that you have bad (contaminated) cya.

I would repeat the test again. This time use something other than the qtip to add the drop. A clean eye dropper or a clean glass or plastic rod would be better.

Then do the cya test normally. Get a consistent reading a few times...you can do this by pouring the solution back into the mixing bottle...repeatedly if necessary. Then add the drop of chlorine again to the already tested solution and retest until you get a consistent result.

If you still see ~40 ppm cya then after the drop see something much closer to zero (filing tube to top) then I think you will have confirmed you have a interfferent, and we should start thinking about some different cya.

Again, someone else (chem geek or others) should probably comment. I wouldn't wait to do the repeat test though...I am very anxious to hear your results.

I ran the tests again just now. The ones I did before must have been done too early in the morning without enough light (it was overcast too) and I the q-tip must have put too much chlorine in the test. I just tested a couple of times the normal way and the vile was completely full and I could still see the dot (barely). So, my CYA is coming in at just under 30. I used a clean eye dropper to add a drop of chlorine to the solution and the test came out exactly the same. My FC continues to hold fairly well considering the amount of CYA I have in the pool.

 

[linen]

So did you get 30 ppm cya prior to adding the drop, then 30 ppm again on the same mixed sample after adding the drop of bleach?

 

[izjay]

So did you get 30 ppm cya prior to adding the drop, then 30 ppm again on the same mixed sample after adding the drop of bleach?

Yes. It was just under 30 ppm for both. I will try raising my CYA once my FC gets down to close to normal range.

 

[linen]

So did you get 30 ppm cya prior to adding the drop, then 30 ppm again on the same mixed sample after adding the drop of bleach?

Yes. It was just under 30 ppm for both. I will try raising my CYA once my FC gets down to close to normal range.

It sounds like your likely measuring cya now, and if there was an interference, it is gone now.

 

[chem geek]

Either the Q-tip approach used too much chlorine or the Q-tip material absorbed CYA (when the Q-tip was added before the CYA test reagent) or melamine-cyanurate precipitate (when the Q-tip was added after the CYA test reagent).

 

[izjay]

I think I finally have my pool back in line. The SWG is able to keep up and this is without the ozonator running. This site (and its users) really helped me solve my problem. I figured I would summarize some things that I now know I did wrong with my pool. I seemed to have a perfect storm where my pool was crystal clear, but it kept eating chlorine and stabilizer. I apologize if any of this is already discussed within other threads on the site.

1. Ozone - I went for the ozonator when I had my pool built. If I had it to do over, I would not have one installed. Mine is now completely disconnected. The companies that produce these units tell you that you can keep your FC as low as .5 ppm. I took this suggestion and kept my FC super low over the past two and a half years. My pool stayed mostly crystal clear except for a few times when I had algae problems. The problem with this low FC (I think) is that funky stuff can still grow in nooks/crannies and in your plumbing. I would suggest that you think twice about using ozone and if you do, make sure you shock your pool every now and then or keep the FC at the low end of the suggested (on this site) range.

The other thing I realized with my ozone unit is that it was restricting the flow of my pump significantly. It has a mixing chamber that requires a redirection of part of the water flow. When I removed this redirection, the pressure at my filter dropped from 10 to 5. At this point, I would rather have the extra flow and not worry about all the problems that come with maintaining an ozonator.

The ozone cell also dies over time. The problem is that you really can't test the output of the cell. So, you just have to replace it when you think it has been enough time. Or, you will see your pool turn green and realize it died. This happened to me once.

2. Robot Pool Cleaner - I have one and it works great. It works so great that I never really brushed my pool. The only time I did was the few times I had the algae blooms. If you have a robot cleaner, you really need to brush your pool every now and then. This is especially true if you have a rough pool surface like Pebble tec (this is what I have). I am going to start brushing mine monthly. I use the robot weekly and it runs for 4 hours.

The other thing about the robot is that it pretty much replaces your pool vacuum. What I realized is that the vacuum line still has water in it. If it is not getting circulated, you may end up with a bunch of funk in that line. I drilled a bunch of holes in the cap that you screw into the vacuum line inlet. I am going to leave a minimal amount of flow going through the vacuum line so that it always has some chlorinated water in it.

3. Water Features - This is another thing that I would not do if I had it to do over. I have a couple of fountains that seemed like a cool idea when I built the pool. I quickly realized that they are loud and splash water all over the place. So, I hardly ran them over the two and a half years that I have had the pool. I would run them every now and then when I had company over. The problem with this is that the water in these lines probably has a bunch of funk growing in it and I was just blasting it into my pool. This in conjunction with me keeping the chlorine low probably wasn't a good thing. Think long and hard about whether you really need a water feature. If you do go with one and is one that you do not run that often, you probably should try and run it on a regular basis to clear out the plumbing.

4. Stabilizer - I definitely had something strange going on with my stabilizer. Either bacteria was eating it up or I had bad stabilizer. The guy that built my pools is having similar problems with pools he manages and he thinks it is due to bad stabilizer from China. I am not sure if this is really the case or not, but it probably doesn't hurt to buy stabilizer made in the USA. You may also want to stay away from places that package it themselves. The place down the street sells it in zip lock bags.

Thanks again for all the help from everyone. I guess I will keep water in my pool instead of filling it with dirt. Of course the forecast for this weekend shows lots of rain. Ha.

 

[jblizzle]

Nice work and thanks for the summary.

Hope you enjoy your crystal clear pool all summer