High TA, CYA, Low FAC and Trying To Understand This All!!!

by Myra
(San Antonio, Texas)

The water looks a little more blue in the pics

The water looks a little more blue in the pics

First of all you are a God-send! I have been researching all your advice to the place where it kind of is making some sense for a new, never before pool owner like me. Bought a home in Dec (San Antonio, TX) with pool its a plaster/marcite pool, 9441 gallon pool, has DE filter had been using pool tabs, but this week we stopped. I shocked once a few days ago, when it was not reading any chlorine and it had been raining, etc. Readings today from pool store:

CYA 100 (before taking the water sample we drained some water, backwashed, etc and refilled, this 100 may be higher I know :( since they read only to 100.
TA 140
PH 7.4
TDS 650
phosphates 500

The pool water looks blue, clear-ISH ... not sparking clear. Our pool is shaded 95% of the day by palms and oak trees (yes, OAK trees!!! the past month I've been a slave to dropping leaves and pollen, I daily, religiously clean out the pool and have a polaris going, etc, seems to be getting better, still some pollen falling here and there, I have 4 girls that swim daily about 3 hrs more or less)

What do I do first to get my levels where they should be, especially CYA, and TA, FAC?
I did purchase liquid chlorine, was told by pool store to add muriatic acid 15 oz and retest in 3 hrs.

I feel overwhelmed! and I don't have the $$ to hire a pool person- I'm it. My husband has little time for this as well :( How do I approach my pool levels? what first? Do I drain again? the pool lady said the CYA sticks to the sides of the pool and I may need to acid wash to lower the levels???? please tell me that is not the case?

Thanks for the question Myra and for the readings. It makes life so much easier.

First, DO NOT add any more chemicals to the water. Your FC will not hold because of the high CYA and here's why. The range is 30 - 50ppm. As the CYA increases through using Trichlor tabs and Tirchlor granular chlorine the FC needs to increase as well. If you allow the CYA to get to 100ppm, you need to run the chlorine at 7 - 8ppm for the chlorine to be effective. When the CYA gets this high the only way to reduce it is a partial drain and refill. There's no chemical to reduce the CYA. If your CYA is at 100ppm, and the range is 30 - 50ppm, then by draining 1/2 of the water and refilling it you'll drop the CYA to 50ppm. You will need to drain 2/3 of the water, refill, FILTER for 24 hours, retest everything and then start making adjustments.

To clear up this size pool should only cost you about $20 - $30 in chemicals. I can't calculate the water because I don't know the rates, but the chemicals are easy.

There are only 2 things you need to concern yourself with right now and that's having a working filter and getting
the CYA to 30ppm with a partial drain and refill. No algaecides, clarifiers, phosphate removers (which are useless unless you had a bag of fertilizer thrown into your pool).

I would encourage you to know the TA and pH of the fill water. If they're high you'll be adding that to the pool which will cause the pool's TA and pH to increase. Simply bring them down with a bit of acid. If the fill water TA and pH are low then add bicarb. It's that simple.

You can NEVER get a good chemical reading 3 hours after making an adjustment, and here's why. The pool flow is calculated in gallons per minute (GPM). This is the filter water loop from the skimmer and bottom drain, through the pipes, through the filter, and back to the pool through the returns. This entire flow is normally 30 GPM. Now let's calculate this out. 30 GPM x 60 minutes an hour = 1800 gallons of filtered water per hour. After 3 hours you've filtered about 5400 gallons of water. 3 x 1800 = 5400. This is only 1/2 of your pool capacity. What happens if you test from a non-treated area of the pool? You're going to get a false reading and then you'll make another adjustment with false data. You've just doubled on the adjustment. Not good. You MUST wait for 1 full turn-over of the water which is normally about 8 - 10 hours, THEN you retest and make another adjustment if needed.

I've never heard of CYA sticking to the pool surface and then needing an acid wash. I've taken care of and cleared up and balanced hundreds of pools since 1999 and have never heard that one. Your situation is fairly straight forward. 2/3 drain and refill, FILTER for 24 hours, test the FC, CYA, TA, pH, and CH and make the right adjustments. I have no idea what the readings will be after the new refill but it'll be easy to take care of. Once the new water goes in you'll be swimming in 4 days and have only given the pool store a few dollars.

Get the CYA, TA and pH in line first. CYA should be 30ppm. TA is 80 - 120ppm and pH is 7.2 - 7.8. Your water is probably hard so no need to add anything there. Then shock the pool a couple of times with liquid chlorine. It's 1 gallon per 10k gallons to increase the FC 10ppm. Your pool is 9400 gallons so 1 gallon per application will do the job.

Broadcast around the perimeter, sweep, and FILTER. Then add another gallon next following evening. Allow the FC to come down to 6 - 7ppm and you'll be ready to swim. Remember that it's not only clearing up the pool but balancing the chemicals. Once you know the ranges it's fairly easy to keep them there without algaecides or clarifiers. I cleared up a cloudy pool AND balanced it in 2 days for $4.50 and that video is on my home page. Very easy to do and you can do it too when you have the right information.

Have a great Summer.


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