Need Help With Lowering PH

[Scottg8580]

Hi there,

new to the board and to owning a salt water pool. Let me give some background information so that hopefully someone can tell me if I am on the correct path. After following the pool builders advice I put all 9 bags of salt into the pool. It threw the salt content to 4200 ppm for a 18000 gal rectangular shaped pool. I drained out approx. 4,140 gallons and replaced with fresh water last Thursday. My new salt reading is 3000 ppm. I noticed on Saturday that I had almost no chlorine even though I had the goldline remote set to 70% for chlorination. I called the pool company back yesterday and was told if my PH is too high, it could be eating up all of the Chlorine. I checked it and it was high, 8.2. I ordered a TF-100 Test Kit yesterday so I don't have all of the specific readings yet. According to the pool calculator I need to put in 30 oz of muriatic acid, which I did. After 4 hours I retested and it had come down to 7.8. I put in an additional 17 oz of muriatic acid. I rechecked this morning and it was still at 7.8. Should I put a 3rd round of 17 oz of acid in the pool?
I'm not sure how long it should take for the equiptment to turn over the water in the pool. I have a Hayward Northstar Main Pump and booster pump for the water features. Any and all help would be greatly appreciated.

Thanks,

Scott

 

[JohnT]

Welcome to TFP.

You probably need to add more acid. Water features, SWCGs, new plaster and high TA can all cause rapid pH rise.

The key piece you are missing is your CYA level. Most SWCGs want it around 70ppm, and not having enough can cause you to have virtually no chlorine in the pool. You'll probably need to supplement with another source of chlorine until you get a handle on your chemistry.

 

[Bama Rambler]

Welcome to TFP

First thing is that pH doesn't "eat" all your chlorine.

TA affects how much acid it takes to move the pH Since you don't have an accurate number Pool Calc can't predict how much it's going to take accurately, so you should go ahead and add some more. I'd shoot for 7.2 if it were me. SWCG's naturally put upward pressure on your pH so targeting it a bit on the low end is usually a good idea.