High CYA & pool draining issues, CYA leaching

[Longboat58]

Hi, The issue with our 15 yr old IG pool is the common issue of high CYA. Today's reading using 50% diluted pool water is off the chart using Taylor 2006 kit. Only took about 3/4" of mixture to cover black dot. I now know why our CYA is high and I have read on TFP what the options are to rectify. Leaning toward a full drain, not too worried about the water table here just East of Austin, TX. I am afraid at our high levels the drain and fill simultaneously approach would take too long and too much of the water would get mixed. RO is expensive, $500-700, water < $200.

Three questions:
(1) Though I could not find mention of it on TFP, I had read somewhere that CYA will keep leaching from the plaster. Is this true and if so how much impact does this usually have?
(2) At our high levels does the plaster need to be cleaned somehow to prevent leaching?
(3) Assuming the water table is not an issue, is it generally safe to do a full drain, any plaster issues?
Thank you so much for your help!

 

[mknauss]

CYA does not leach into the plaster.

Biggest issue with a full drain this time of year is letting the plaster dry out in hot sun. It can crack and fail.

Why do you not think an exchange would be a problem? Can you post or share a full set of test results from your test kit?

 

[Longboat58]

Hi, I was thinking that if we used a pump similar to the ones that have been discussed that move about 6 gpm that it would take about 70 hours for a full exchange. Seems that over that long of a period the 2 water sources would get mixed reducing the effectiveness quite a bit. Regarding the leaching, my neighbor who had the same issue, drained his pool, refilled, replaced the filter cartridges and said the CYA started at 50 with nothing added. I will post full test results tomorrow. Thanks.

 

[Leebo]

If I were a gambling man I’d place bets that he was either using test strips or a pool store for his “testing.” CYA in the plaster is pure hogwash.

 

[Donldson]

If I were a gambling man I’d place bets that he was either using test strips or a pool store for his “testing.” CYA in the plaster is pure hogwash.

My first bet would be on test strips. A few people have reported (impossibly, I might add) 50 CYA on new fills with those things. Absolute junk, they are.

 

[zea3]

Yep, if you have tests strips, just for grins test your water straight out of the faucet. You should have a little FC, a TA result, a CH result, and a pH result. CYA should be 0, no change on the strip whatsoever. It is also possible your neighbor had astronomical CYA levels and did not drain the pool 100%. The test only reads up to 100ppm. It is not uncommon for someone who used dichlor/trichlor exclusively to have CYA levels of 200ppm or more. In cases where super high CYA is expected we recommend diluting the pool water sample with tap water. 1 cup pool water and 1 cup tap water mixed together, then use that as your sample and test normally. Double the result. It is not as accurate as the regular test but it does give a ballpark figure that's good enough for deciding how much water to drain.

If you can set up you pool to drain in the late afternoon and evening and refill overnight that will cut out a lot of the risk of letting the plaster get too hot and drying out. If you have a big enough tarp and a way to secure it you could shade part of the pool to cut down on direct sun beating down on the plaster.

 

[Longboat58]

Thanks for all the comments. I'm unsure how he tested the water to arrive at a CYA of 50. Good to know that CYA doesn't leach out. Would hate to do a full drain and find that the CYA is rising. As far as protecting the plaster during a full drain, I would try as zea3 suggested and do the refill over night. Would a sprinkler also work for keep the plaster cool that is in the direct sun?
My test results are below but I have not been too concerned since I thought I was going to be doing a drain or exchange. Thanks
FC – Free Chlorine 13 ppm
CC – Combined Chlorine .5 ppm
pH 7.2
TA – Total Alkalinity 100 before CYA adj
CYA – Cyanuric Acid, as stated earlier, is off the chart even with diluted 50%
CH > 400

 

[IceShadow]

Dilute it further. One cup pool water, three cups tap. Try again. It would be good to have a target.

If that doesn’t work try one cup pool water to seven cups tap water and multiply by 8.

 

[Donldson]

At this point I wouldn't suggest further diluted testing. The margin of error increases significantly once you get past the 50/50 test. A very significant water exchange is going to be required regardless and the 2006 have a pretty limited number of CYA tests, so best not to waste them.

Also, just from the TA comment, we don't worry ourselves much with Adjusted Alkalinity.

Good luck with the water exchange, just remind yourself that now that you found TFP this should not be something you will likely ever need to do again!

 

[IceShadow]

At this point I wouldn't suggest further diluted testing. The margin of error increases significantly once you get past the 50/50 test. A very significant water exchange is going to be required regardless and the 2006 have a pretty limited number of CYA tests, so best not to waste them.

Also, just from the TA comment, we don't worry ourselves much with Adjusted Alkalinity.

Good luck with the water exchange, just remind yourself that now that you found TFP this should not be something you will likely ever need to do again!

Listen to this guy, not me. ;D

 

[Longboat58]

Thanks for all the input. Getting a quote on RO but may end up just waiting until the temps here cool down some and then just do the full drain, if we can manage it that long.