Alkalinity

[bobgard]

I bought a house three years ago with an older in-ground pool so I am a relative newcomer. I consistantly have a problem keeping the ALK in the 80-120 PPM range. I recently bought a Taylor K-2006 tester so I could get reliable numbers. My pool ALK normally wants to stay in the 140 - 200 PPM range; since my fill water is from a well I decided to test the water from the tap (TC 0.0; pH 7.4; ALK 325; calcium hardness 180 and CYA 0.0) my pool water as tested is FC 24.0 (because of an algea bloom) CC 4.0, TC 28.0; pH 7.8; ALK 140; CH 380; CYA 100. The CYA got high because I was using a lot of stabilized shock and it will only come down from dilution. My question is since the fill water ALK is so high going into the pool should I keep trying to keep it in the 80-120 PPM range. The pool water temp is above 90 degrees.

Bobgard

[aylad]

Since the alk is so high, you're going to fight an endless battle trying to keep it lowered. If it's not causing you problems, and your pH is stable, then I would leave it alone.

[bobgard]

Thanks for the info on TA. After further reading on other threads with a simular problem they stress not using cal hypo as it raises TA. Based on my high CYA reading of 100PPM, what type chlorine should I use?

[aylad]

We generally recommend plain, unscented bleach. If you'll post your pool's volume, then we can help you figure out the dose that you'll need, but generally 1 gallon of 6% bleach will raise the FC by 6ppm in 10K gallons of water. In my pool, I use one of the large WalMart jugs (1.4 gallons, I think) every two days to maintain 8 ppm of chlorine. (My pool is high CYA, too, but intentionally).

Now, if you tell the pool store that you're using bleach in the pool, they'll usually go into hysterics and emphasize that bleach is not to be used because of risk to the liner....but I have yet to have a pool store employee be able to tell me why it is that using liquid chlorine that they sell in pool stores (which is 12% sodium hypochlorite) is good for the pool when bleach (which is 6% sodium hypochlorite) is so BAD!! :)

Janet

[giroup01]

I faced a similar problem with fill water from a truck at one of my clients, as I recall TA was 360 or thereabouts, pH above 8. I eventually brought it down to 80-100 ppm with constant additions of pH-. Keep it down else you risk scaling at the waterline.

Cal Hypo doesn't raise TA it raises CH.

[bobgard]

My pool is an in-ground, gunite or concrete with palster. It's shape is like a two-ball snowman and the end being lager. It's 32 feet long X 16 feet on deep end and 18 feet at shallow end. The depths are 3.5 feet shallow end and 8.5 feet deep end; so my guess is it is 25,000 gallons. My CYA is 100-120PPM and water temps in the lower 90s, so I'm trying to keep FC between 8-12PPM. I really appreciate the help and my pool has really been look great, good color and clarity.