decraesing alkalinity without decreasing pH

Jul 28, 2007
Please help me. My pool is somewhat cloudy. i got a test kit it said my alkalinity was high (270ppm; but the pH was ideal 7.6). went to pool store and they told be to slug the pool. I added 2 1/4 cups of ph down ( in 1 gallon water slurry) to a 1250 gallon above ground pool. It decreased the alkalinity to 120ppm- Great but now the pH was below 6.8. I had to raise the pH back up with pH up (sodium carbonate) and know the pH is 7.6 but the alkalinity it back up to 270ppm. I basically am going in circles. We are on well water, i added calcium stabilizer and chlorine shock but that is the only thing that has every been in the pool. It is also usually covered. How can you decrease alkalinity without decreasing pH or once you decrease alkalinity how do you raise pH without raising alkalinity again? Can you help me????

edit - Moved by Divnkd101 07/30/07


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
The correct way to lower the alkalinity is to lower both the PH and TA with acid till PH is between 7.0-7.2. Then aerate the pool to raise the PH backup without changing the TA. Repeat this cycle until the TA is where you want it to be. To aerate your pool you can use spa jets, waterfalls, fountains, kids playing in the pool, rain, aimming the return up at the surface of the water, an air compressor, etc.


LifeTime Supporter
Jun 14, 2008
Bruce Peninsula - Ontario
Thanks Jason, it,s been 5 or 6 years since I built our pool and we have enjoyed it thanks to TFP, this was something I forgot and now remember why I made that fountain from PVC pipe. Pool is finally up to my comfort temp level and soon the numbers will be perfect! Thanks


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
Welcome back! :wave:

A couple things in your post jump out at me.

1) How about a full set of test results? If you have high CYA or low chlorine for the CYA, you could be fighting an algae bloom. It gets hazy long before it gets green and chunky. You want to stop that quick if that's the case.
2) You're adding Calcium to the water. That can cloud things for a few days when combined with high alkalinity. Literally, you growing chalk dust in your water!
3) Your vinyl pool doesn't need Calcium. You could have zero and the pool wouldn't care. It's plastic! A concrete pool needs some Calcium to keep the water from etching the finish. Your pool won't etch. The pool store just ripped you off selling you unnecessary stuff.
4) The slug method doesn't work, as you've seen for yourself. Here's some scientific proof you can read if you need some help getting to sleep tonight....
5) The proper way to lower TA is here. Anything you can do to get the surface of the pool bubbling will help. If you need to add water, don't just drop the hose in. Hook it to a sprinkler or a spray nozzle and hang it over the lip so it sprays down on the surface and makes it bubble.
6) The common chlorine "shock" powders add stabilizer (CYA) which means you need more chlorine to maintain enough active stuff. If you add it using more powdered chlorine, you raise CYA even higher, which means you need even more chlorine to keep up, which raises CYA even higher, see where this is heading, right? Spiralling out of control.

Have you read anything in Pool School yet? I'd suggest you start with the first two articles on this page.
Then read this page so you learn our strange language. And then maybe take a look at some of the other articles on this page. Or just browse around. You'll learn answers to things you haven't even thought to ask yet.