Chemistry Help: TA, CYA & FC Lifespan

RJ2920 · May 28, 2012

I purchased a foreclosed home last year and decided to get the small 10,000 gallon backyard pool relined and open it this year. While I do not have any major aesthetic problems (yet) I am having a difficult time maintaining a proper chemistry - mainly lowering the TA, maintaining steady FC levels, and introducing CYA to the water. First, here are my current numbers (as per the 6way HTH test kit from Wal-Mart):

FC: 3ppm (I just added a gallon of HTH Liquid Sodium HCL 10% about 90 minutes ago, FC will be at 0 in 2-3 more hours as it is 89 and sunny today in Northern Indiana)
PH: 6.8 (I just added 1gallon of 31.45% Muriatic Acid to deal with my high TA 90 min ago, before this PH was at 7.5)
TA: 240 (in lieu of the 1 gal addition of Muriatic acid which sent my PH spiraling downward)
CYA: 0 (I use a floater full of 1" HTH Trichlor tabs which I thought would increase CYA while decreasing TA - after 1 month neither have happened)

About a week ago, the water had become cloudy and I could feel, but not see, algea beginning to grow on the sides. I scrubbed, vaccumed, shocked and used a clarifier and there is no more film and the water is crystal clear. Since then I have been adding 1 gallon of 10% chlorine daily and water has remained crystal clear and no algae is detectable. I want to know how to bring my chemistry to proper levels and increase the lifespan of my chlorine.

I have never owned a pool before, so any info is appreciated! Please let me know if I can provide any more information.

duraleigh · May 28, 2012

1. Adding muriatic acid is not the correct way to lower TA - There is a good article in pool school that will walk you through the process.

2. Add CYA separately. You can buy enough at HD,Lowe's Pool store, walmart, etc. might be called stabilizer, conditioner, CYA but it is all Cyanuric Acid (check the label) Calculate and dose enough to get to 40ppm

anonapersona · May 28, 2012

Read Pool School. Take notes on the section, Test Kits Compared, then order one of the top picks (I have the TF-100 plus SpeedStir and highly recommend both)

Start a Pool Log book and record all equipment specs and pool details, then begin recording every water test and all chemicals you add along with the reason for such.

I preferred the HTH Conditioner from Walmart over whatever brand I got at the pool store, HTH dissolved faster. Get that CYA level in order and you will be able to keep chlorine levels better and thus fight algae.

Richard320 · May 28, 2012

TA is the last thing to fix. You work on that when everything else is under control and you're bored.

I concur with the others. Add CYA to get up to 40. You likely have some from the pucks already, so aim low, it will probably end up in the 50-60 range. You can always add more. That will help hold the FC up all day. Expect to lose 2-3 ppm in a perfect pool; more if there's a lot of sweaty, dirty kids in it, or a lot of dust blowing in. Just keep adding whatever it takes to stay above 5.

In about a week, you can test CYA again. By then, your pH should have recovered. Don't rush it! If you lower pH too much, your water may etch metal parts in the heater or filter. You don't want that, it gets expensive.

RJ2920 · May 28, 2012

Thank you, everyone, for the information and replies. Some information I realized I left out is that a neighbor's tree is constantly dropping thousands of mini leafs into the pool during even slight winds, which is probably also contributing to my CL consumption.

Just a couple more questions:

1. Why was adding muriatic acid was not the correct way to lower TA? I read the pool school article on lowering TA and thought that was the way to go, which will bring down TA and PH, and then aerate to raise PH back to normal without raising TA.

2. I thought the Trichlor tablets would have added some CYA to my pool at this point, why haven't they?

3. Is their a specific brand of CYA I you would recommend for my specific situation?

Thanks again for the info.

duraleigh · May 28, 2012

1. It is the process of acid/aeration that PERMANENTLY lowers TA. As you discovered, simply adding acid drove your pH too low. You needed the aeration to raise the pH back up and leave the TA where it ended up.
It is important to understand that you have to do both to make a permanent difference.

2. The Pool Calculator will tell you the affect of adding trichlor tabs. It is hard to get an initial dose of CYA from a few tabs.

3. It's all pretty much the same....should be a high (96%+) percentage of CYA with no filler but I think allof themare.

Richard320 · May 28, 2012

RJ2920 said:
1. Why was adding muriatic acid was not the correct way to lower TA? I read the pool school article on lowering TA and thought that was the way to go, which will bring down TA and PH, and then aerate to raise PH back to normal without raising TA.

It is the correct procedure, but you should do it in steps, not all at once. Aim for 7.2 pH, aerate it until it rises, then drop it again. Doing it all at once knocks the pH too low, which attacks metal.