pool chemical problems

Pool-in ground gunite, 10-12,000 gal, Triton II sand filter & Centurion 1.5 hp pump. I am going thru chlorine tablets like crazy when in the past summers it would only take approx. (1) 3" tab per day in a floater-now I am using two floaters and approx. 2 chlorine tabs/day per floater and still can not keep the chlodine level up to 1ppm. In the past a 40 lb bucket of 3" chlorine tabs would last 3 months and now I have gone thru one bucket in 1 month. I had my Cyanuric Acid checked and it is about 120. I also am having trouble trying to raise my PH above 7.2 (water at tap is 7.2) and have dumped several boxes of Mule Tide as suggested over a wk with highest reading PH at 7.4. We are on water restrictions in West Tx and can not drain the pool or even drain half to lower the CYA to a more acceptable level but I am not sure that will cause the high chlorine usage? I have also been using some bleach to try to keep from using so much chlorine tabs.

Hi, and welcome to the forum!!

With the weather this hot (I'm near Shreveport, LA, so I have basically the same climate as you), it won't take much at all for an algae bloom to get started, and if you've spent any time at all with a CYA of 120 and chlorine less than 8 ppm, you probably are losing most of your chlorine to an impending algae outbreak. You need to stop using the trichlor tabs at this point, and go strictly to non-stabilized chlorine (bleach!), otherwise your CYA levels are going to keep rising. See the "best guess chlorine chart" linked in my sig for more information on where your shock level and regular chlorination levels need to be with a CYA that high. Also, the trichlor is what is driving your pH down--once you stop using the trichlor, you shouldn't have any problems keeping it above 7.2 just by pointing your return jets upward so they ripple the water.

You need to shock your pool up to 25 ppm, and hold it there by testing and adding whatever chlorine is needed to get back above 25 ppm, until you can go from sundown one night to just before the sun hits the pool the next morning, and lose 1 ppm or less of chlorine. At that point you can let it drift back down, but with a CYa that high, never let it get below 8 ppm.

Running a high CYA pool is not necessarily a bad thing, and it's about the only way to manage a pool without losing too much chlorine to the sun. I purposely run mine at 80-90 ppm because I lose less chlorine daily there than at lower CYA levels, and it allows me to dose evern 2-3 days instead of every day. So a CYA of 120 is not necessarily "unacceptable", and I would have no problem with running it just the way it is--you just have to get rid of that chlorine demand by shocking. No more trichlor tabs!!

Use bleach to shock the pool as Janet advised above. In your pool, each quart of plain unscented 6% bleach will add approximately 1.5ppm of chlorine. Use that as a reference to help you figure out doses of bleach to use.

Can you tell me approx how much bleach to get to 25 ppm as I don't have a test kit that will go over 5ppm unless I double it with DI water?

12,000 gallon pool => PF 12 (120,000 gal = 1,000,000 lbs H2O)

25 / (12 x 0.5 lbs Cl2 per gal 6% bleach) = ~ 4 gallons of PLAIN 6% household bleach. However, if you have a CYA ~ 120 ppm, I'd add 6 gallons. And yes, you can still swim. Just don't wear any new fashion swim suits. People are much, much more chlorine resistant than Lycra!

BUT . . . you are going to continue to have problems without an accurate test kit. I'm guessing your "120ppm" comes from a dealer's electronically read 'guess-strip'? No matter how you read 'guess-strips' they are NOT accurate. Here are your testkit options:

HTH 6-Way Test Kit @ Walmart
Taylor K2006A (3/4 oz bottles) @ Amazon
Taylor K2006C (2 oz bottles) @ Amazon

The Walmart kit is a subset of the Taylor, but with OTO testing (good to have on hand for daily use) and it does have a CYA test. If you can get it now, and order the K2006 (they are NOT available locally!). You'll need to do a 1:1 dilution to test 120 ppm CYA, so buy a gallon of distilled water from Walmart when you get the kit.