How to lower Alkalinity without acid

I have a round 24' pool 52 inches high, with a hayward gas pool heater,hayward sand filter. I use a lamotte pro 9 test kit. I had some mustard algae I have been trying to get rid of. My cya was around 80+. I drained over 50 percent out. After refilling the CYA is 33. FCL-3.27,TCL-3.33, PH-7.5, Alk-201, CH-LO. How can I lower the TA without raising the CYA again. I just switched to liquid chlorine so I don't add any more acid. I am on a well and the well water tests ALK at 210, so it will be a constant battle. Thanks

1. Using acid doesn't raise the CYA. Muriatic acid, diluted sulfuric acid, or the crystalline sodium acid salt of sulfuric acid (sodium bisulfate) all are used to lower pool pH levels; none contain CYA (cyanuric acid).

2. Why do you want to lower your alkalinity? Is it causing you a problem? If your calcium is low, and your pH is stable, alk=200 isn't necessarily a problem.

3. There's no telling what your CYA level *really* is -- test strip readings (even by an electronic gizmo) are horrendously inaccurate.

4. See the Best Guess page (link in my blue signature block) for an explanation of the relationship between chlorine and CYA, and why that's an issue with mustard algae.

5. Using borax is the easiest long term way to reduce your pool's tendency to get mustard algae. Once you add it, it's in your pool permanently. With a sand filter, you'll lose a little each time you backwash, but it won't take much to keep up. 12 boxes of borax and 4 gallons of 31% muriatic acid should get you there. That should be a bit more acid than you need, but with a Alk=200, your pH will tend to drift up anyhow.

6. Oh, yeah. You can't lower alkalinity without acid. Doing so would be sort of like flying without wings or making bread without grain.

Thank you for the information. I use a lamotte pro 9 test kit. I drained about half the pool and refilled it so I wouldn't have to use so much chlorine to shock. I added a quart of muriatic acid and the levels now are: FC-4.19, TC-4.27, PH-7.4, ALK-193, CH-27, CYA-33. I switched to liquid chlorine. I wanted to make sure the CYA levels wouldn't rise and be back where I started. The reason I wanted the alkalinity down was because of my pool heater. I didn't want to have scale inside of it. Do I need higher calcium because of the heater? What is the best way to aerate to raise the PH after acid: water fountain or air injected into the water? Thank you

+ Hayward will tell you need CH > 100 ppm. I doubt that that's true, but it won't hurt.

+ With a heater, you do want lower ALK.

+ I don't know which would be more effective aeration; I believe either would work fine.