Chemical Yo-yo

[CHIP73]

(First Post)
I have been getting a lot of advice from this forum over the past 2 years since I bought my first home with a pool. You all have helped me a lot and I thank you very much. But now I have a problem that I just can’t figure out. Here is a quick rundown of what has happened. This past winter I covered my pool and had the pump running 4 hours a day. I would brush it once in awhile and vacuum it about every other week. Everything was fine. Then I went out of town for about 3 weeks and at some point the chlorine generator stopped working. When I got home I had a pool full of mustard algae. I Replaced the chlorine generator, got rid of the algae, cleaned all the pool equipment, and my pool looks great. Now here is my problem. Two weeks ago the alkalinity was over 300. I used several gallons of muriatic acid to get it down to 120. That also lowered the PH to 6.8. Then I added 10lbs of soda ash. That brought my ph up to 7.4 and the alkalinity back up to 280. I never had a problem before the algae attacked and never had issues balancing the chemicals. What happened and how do I lower alkalinity and raise the ph?

 

[Texas Splash]

Hello and welcome to TFP!

What happened and how do I lower alkalinity and raise the ph?

Once the pH reaches 7.8, smack it down with acid to about 7.0, then "aerate" only. No chemicals. Aeration will raise the pH and leave the TA alone.
Pool School - Lower Total Alkalinity

 

[GOONiE]

if you want to raise pH... only use borax. it wont raise TA. But pH should rise naturally when you aerate. Get a fountain installed in a jet or point the so they break the surface water. This will raise pH.

 

[CHIP73]

Ok. When I went outside this afternoon I did a double take when I saw my pool had a purple tint to it. Purple cyanurate! I ordered a product called C-U-Lator to remove the metals in the water. I think that was the root of the problem and throwing off my ph and akalinity tests.

 

[CHIP73]

Ok. I got the purple cyanurate under control and the C-U-Lator did a great job of taking care of the metals I’m the water. My alkalinity is 330 and Ph is 7.4. Do I add muriatic acid to lower alkalinity and then aerate the water to raise the ph?

 

[Dirk]

Ok. I got the purple cyanurate under control and the C-U-Lator did a great job of taking care of the metals I’m the water. My alkalinity is 330 and Ph is 7.4. Do I add muriatic acid to lower alkalinity and then aerate the water to raise the ph?

Yes. Use PoolMath to figure out how much MA to lower pH to 7.2, then aerate to 7.8. Repeat until you reach your target TA (alkalinity). If the aeration is slow going, return to TFP for ideas, you'll find a lot of solutions. I built my aerators out of PVC and screwed them into my returns.

 

[CHIP73]

I’ve added 3 gallons of MA and alkalinity went from 300 down to 220. The ph dropped to 6.8. Ive got the fountain and the jacuzzi jets aerating. Do I add more acid or wait till the ph comes up first?

 

[mknauss]

Wait until the pH reaches 7.5 or above. Then repeat, lowering pH to 7.2 (based on what PoolMath says with your new TA)