Ongoing issues

[CarlD]

The pH increaser is almost certainly Sodium Carbonate, also called Soda Ash, but better known as Arm&Hammer Washing Soda (not baking soda).

It will increase your total alkalinity. If your pool is vinyl, it shouldn't be a problem. If it's concrete, tile, etc, I wouldn't add it. Instead, aerate your water to raise your pH without increasing total alkalinity. You can simply point the return at the surface so it bubbles.

The 12% liquid chlorine is good stuff. You'll get an increase in Free Chlorine of 12ppm/per gallon/per 10,000 gallons of water. So if your pool is 30,000 gallons, you need 3 gallons of the LC to increase FC by 12ppm. You want to get your pool to an FC level of 15ppm given a CYA level of 21ppm. So she MAY have told you the right thing...depending on the volume of the pool.

If your liner is vinyl, you want to stay at the recommended shock levels in Ben's Best Guess table. If you have a hard-sided pool, you can exceed it and speed up the algae killling.

Carl

Correction: You have 20,000 gallons, vinyl. 4 gallons of 12% will increase your FC by 24ppm--too much for a vinyl pool with a CYA of 21. It can bleach your liner. IF you don't care about that (like me, with an old liner) 4 gallons should work spectacularly well. (that's what I did a few weeks ago, but I don't care about my liner fading--it's faded already). However, if it's a newer liner, you'll want to add 2.5 gallons of LC. That should boost your FC to 15ppm, which is what you need.

[jeremyweber]

Yes the pool is vinyl and my best guess is around 20k - 22k in water volume. So if I use the 2.5 gallons, how much of the ph plus should I be using? And when ( before or after the chlorine ).

[CarlD]

Well, I'd use about 1/2 of it with the filter running, wait an hour and then test pH. If you are still low, add the rest. But if you are over 7.2 to 7.3, I wouldn't add more, at least not now. Just aerate.

Carl