Trying to get the CYA under control.

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LordBob

LordBob

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Gold Supporter
Jul 13, 2018
59
Redlands, California
I recently have been maintaining, or trying to, a mobile home community pool. I have only maintained a private back yard pool of mine before. A few days ago the county health department closed the pool citing unsafe chlorine levels (easy enough to take care of just added some chlorine), and high Cyanuric acid (119, the county requires it to be under 100). After doing some research, and talking to the pool guys at my local pool store, I found out what CYA was and the only way to reduce it was through dilution. The guy at the pool store suggested a 2/3 drain and refill. After draining and refilling, I skimmed the pool and let the filter run over night, I took in a fresh water sample this morning and the CYA was 128 which is higher than it was before. I just wanted to get another opinion. he now suggests I pour in a gallon of acid let the pump run over night scrub the walls and bottom of the pool, drain completely and start from scratch. He says that the CYA has absorbed into the plaster and coated the pipes and that's why the CYA went up, stating the water was saturated and when the clean water was put in it basically sucked it out of the plaster and pipes.

The pool was replastered a year ago this month. I wasn't the one that set the pool up for this season and wasn't involved with the setup and curing process of the replaster. We use chlorine granules (which I just recently learned contain stabilizer), having to over chlorinate especially during the hot days in So Cal.

What would you guys suggest I do?

The pool is a rectangular 25,000 Gal, IG, Plaster, DE Filter, Pentar FNS Plus, Water is just city spigot water.
 
:wave: Welcome to TFP!!!

Where did the 119 and the 128ppm CYA test results come from? That is not possible so one of the tests was wrong.

CYA does not absorb into the plaster.

Just stop talking to people in pool stores and you will be way better off :D

I suggest you invest in one of the Recommended Test Kits and start testing your own water and post up the results here.
 
Welcome to the TFP pool! :splash:

First, the guy at the pool store said
He says that the CYA has absorbed into the plaster and coated the pipes and that's why the CYA went up, stating the water was saturated and when the clean water was put in it basically sucked it out of the plaster and pipes.
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I'll be nice, he has no idea what he is talking about. CYA doesn't work that way.

The problem is the testing. CYA tests above 100 are just a guess, not very specific contrary to what the pool store says. Not much credence is given to pool store testing around here. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing. Additionally, we find that many times pool store employees primary goal is to sell stuff, not necessarily get your pool in perfect condition. As to whether that is because of improper training, lack of knowledge or just to sell stuff I will leave up to you. Plus, the results of their "testing" is used to convince you that you need to buy things. Why do you think that testing is free?

More dilution is required. Folks who have posted here have found their CYA was several hundred, not the lower numbers told to them by the pool store.

To know what is going on with your pool we need accurate test results we can trust, and those don't come from a pool store. We base our pool care system on your personal accurate testing and only adding what the pool needs, when it needs it. To do that you need your own accurate test kit. Order a TF100 test kit.

The only other real option for a test kit is a Taylor K-2006-C. Be careful comparing prices because the K-2006 comes in sizes, designated by a letter. The basic K-2006 has .75oz bottles. You need to get the K-2006-C to get the larger bottles that you want. Even then it is a little short on the reagent & powder for the FAS/DPD test.

While entirely optional, I also have the SpeedStir and Sample Sizer. They speed testing and accuracy.

Now, your real problem - the source of the CYA. I'm going ot go out on a limb here and guess, but you probably have a Pentair 3" tab erosion feeder that you keep stocked with tabs. Once, or maybe twice a week you throw a couple/few bags of "shock" into the pool. I bet the pool guy who has sold you those tabs and shock forgot to tell you that they are almost 50% CYA.
 
The CYA results came from the pool store from the sample I brought in for them to test. The 119 was before I did anything to the pool, the 128 was after the 2/3 dilution. The whole scenario didn't sound right to me either, that's why I came here :eek:)

Currently we have a basic CH, PH test kit, it also does acid demand and total alkalinity. I recently bought some test strips that you match the color on after dipping it in the water that tests CYA, FC, and a few other things. After the health inspector closed the pool and doing some research I realized I needed a better test kit than what we were currently using, but all the pool store had was these test strips.
 
LordBob said:
I realized I needed a better test kit than what we were currently using, but all the pool store had was these test strips.
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You were actually better without the test strips because you still had money in your pocket. We call test strips "guess strips" because the answer they give is just as good as a guess.
 
The pool guy actually hasn't tried to sell me anything, not to say that it isn't his eventual intention, and to his credit, he told me that test results that high are inaccurate, and he's had people with the same problem that ended up having CYA 500+ after all was said and done. We do have the 3" tab erosion feeder, but I haven't put any tabs in it, and am pretty sure none have been put in since the initial start up last year, although I did open it the other day after the closure and it did have a strong chlorine smell. I haven't shocked the pool at all since I have taken over, that's not to say it wasn't done before. I have been doing the pool for about 2 months. I did just order the TF100 test kit you suggested.
 
So, having an unreliable test from the pool store, where should I go to get a test done that would be accurate until the test kit comes? This is a community pool and people aren't happy LOL. At the same time I don't want to call the inspector out again till I have things under control.
 

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If the health inspector got a CYA reading of "119" his is using a digital meter, probably a Lamotte ColorQ. Unfortunately while they give very specific results, accuracy isn't one one of their hallmarks.
 
Just keep adding a gallon of 10% liquid chlorine daily until you get your test kit. That will at least keep things in a holding pattern without the pool turning green. Once you get the kit, run all the tests, post them here, and we'll get you squared away on how much more to drain the pool before the refill. Also, don't add any hard forms of chlorine to the pool from now on. Only liquid chlorine. All hard forms of chlorine (tablets, powdered shock, granules) add either additional CYA or calcium with every dosage. The chlorine gets used up, but the CYA remains in the pool. So you redose with more of the same, and guess what, before you know it your CYA is out of control. Then you've got no choice but to drain some water to dilute it. Sound familiar?
 
DeanP66 said:
J The chlorine gets used up, but the CYA remains in the pool. So you redose with more of the same, and guess what, before you know it your CYA is out of control. Then you've got no choice but to drain some water to dilute it. Sound familiar?
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LOL Yes, unfortunately something I learned too late. I don't think the guy that usually takes care of the pool knew either, because that is the chlorine they have always used.

- - - Updated - - -

Can I use the pool pump to empty the pool, or would that be a bad thing? I think I know the answer, just trying to not have to rent and mess with the submersible pump.

- - - Updated - - -

tim5055 said:
If the health inspector got a CYA reading of "119" his is using a digital meter.
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The 119 number came from the pool supply store test, but I am sure you are right, I can't see them wanting to spend much time testing.
 
You are best off to get a sub pump from Harbor Freight, Home Depot, etc to drain the pool.

As it is summer, it is not a good idea to leave plaster exposed to hot sunshine as it can crack and fail.

An option is to do a water exchange.
You can exchange some water without draining.

If you place a low volume sub pump in the deep end and pull water from there while adding water in the shallow end you can do a fairly efficient exchange. That is assuming the water you are filling with is the same temperature or warmer than your pool water. If your fill water is much cooler than your pool water, then switch it. Add the water to the deep end (hose on bottom) and pull water from the top step.

The location of the pump and fill hose may change if you have salt water, high calcium, etc.
In my pool, with saltwater and high calcium when I drain, I put the pump in the deep end and hose in shallow end. The water in the pool weighs more per unit volume than the fill water from the hose.

Be sure to balance the water out and water in so the pool level stays the same. Also be sure your pool pump is disabled during this process. Once started do not stop until you have exchanged the amount of water you wish.
 
Trying to get the CYA under control. Part 2

Hi Again guys,


I just got my TF-100 test kit today, and tested the water, (Brief recap: I have already replaced 2/3 of the water, with the pool supply store telling me my CYA was 119 after the pool being closed by the health department for High CYA. CYA after dilution was 128 according to the pool supply store That's when I came here)

These are the results of the test:

Free Chlorine: 3
Combine Chloramines: 0.5
Calcium Hardness: 600
PH: 7.5 Acording to the regular 5 drop test
Total Alkalinity: 150
CYA: 100+ dot disappeared 1/8" below the 100 line

Should I just empty the pool totally and start from scratch, I understand that a CYA test above 100 is inaccurate as far as how much over 100 it is. I would just hate to do a 2/3 dilution again and it still be high.
 
Before you go any further, now that you have your own TF-100, I would do a "diluted" CYA test following the Pool School - CYA page starting at Step #8. Once you double the result to get your true CYA, then you will know how much water to exchange. That should also help lower your high CH as well. Let us know how it goes.
 
Try a diluted test. While the full instructions are in the Pool School, here is the short version. Mix 50% pool water with 50% tap water. Use this mixed sample as your test water. If still at a 100 you will need to dilute more. The problem is that when doing a diluted test not only do you multiply the rage of the test you multiply the error rate of the test, so results are a ballpark - not an absolute. Here is a great chart by JamesW to explain dilution rates and what you multiply the results by to get an approximation of your CYA level.

Pool water......Tap or distilled water.........Multiply result by

....1...................1................................2
....1...................2................................3
....1...................4................................5
 
tim5055 said:
Mix 50% pool water with 50% tap water. Use this mixed sample as your test water.
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That was going to be my next question right now. Also Thanks to whoever linked my threads my post for me.

Maybe a stupid question, but if I, say, take a 1/2 cup of pool water and 1/2 cup of tap water and mix them, wouldn't that be the same as diluting the pool 50% I'm not grasping the multiplying by 2.
 
LordBob said:
That was going to be my next question right now. Also Thanks to whoever linked my threads my post for me.

Maybe a stupid question, but if I, say, take a 1/2 cup of pool water and 1/2 cup of tap water and mix them, wouldn't that be the same as diluting the pool 50% I'm not grasping the multiplying by 2.
Click to expand...
1/2 cup of pool water and 1/2 cup of tap water mixed together becomes your "pool water" sample. What ever answer you get on the tube is multiplied by 2 to see what your CYA is.
 
LordBob said:
That was going to be my next question right now. Also Thanks to whoever linked my threads my post for me.

Maybe a stupid question, but if I, say, take a 1/2 cup of pool water and 1/2 cup of tap water and mix them, wouldn't that be the same as diluting the pool 50% I'm not grasping the multiplying by 2.
Click to expand...

Your CYA is out of testable range. So by diluting the pool water 50/50 with tap water, you can hopefully get the test within the range of your test kit. But you have to multiply the test result by 2 because only half the water is pool water. Tap water has zero CYA.
 

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