PH Question

[aylad]

In previous years I have always had trouble with my PH rising. I would add muriatic acid & within a day or two it would rise back up. Is there anything that can prevent this? I have a 12,500 gallon fiberglass pool.

What is your Total Alk, and do you have a waterfall/fountain/anything else that aerates the pool water? Aeration of the pool water will make your pH rise, although at what rate really depends on your alk. Also, what form of chlorine are you using? Bleach has a higher pH, while trichlor/dichlor is lower. Depending on your CYA level, you could use trichlor to help chlorinate and keep the pH down, until yourCYA level rises to where you want it.

What is the pH of your fill water? Some pools have a pH at which they like to "stay"....if left alone, the pH in my pool will invariably go to 7.8 and then stay there....unless I'm using trichlor or acid. In that case, it's just easier to live with a slightly higher pH than it is to fight it.

Janet

[cnk]

I haven't uncovered & tested yet this year, but as soon as I do I will post my #'s. I never thought of testing my faucet water. I will do that. Also, I've always been confused on when to use Borax. I've never used it, could someone educate me on it. I just use liquid bleach & muriatic acid. I had the same problem when I used Baquacil.

[Watermom]

Borax is used when you need to raise your ph. Since your ph tends to run high, you don't need to use it.

[aquarium]

When you test your tapwater be sure to let it sit in an open container for 24 hours before trusting the test result. Some water treatments drive all the CO2 out of the water to make it less corrosive to the pipe system. After sitting out for 24 hours that water will take in CO2 from the atmosphere and reach a stabilized pH level.

[cnk]

Thanks Guys! We are on well water.

[chem geek]

There is a technical discussion at this thread in the China Shop that explores why pH rises and what can be done about it. It's a long thread, but the bottom line is that the pH normally rises due to the outgassing of carbon dioxide. Pools are intentionally over-carbonated (like a tasty beverage!) as part of the pH buffering system from carbonates. When carbon dioxide outgasses (i.e. leaves the pool water and goes into the air) it raises the pH of the pool water.

This outgassing process is accelerated by aeration of the water, by lower pH, and by higher TA. This table gives a rough idea of relative rates, but aeration isn't part of the table so the actual rate of pH rise will be depend on the aeration. An SWG actually aerates the pool as the hydrogen gas bubbles that are produced are a form of aeration and pull out the carbon dioxide faster so typically SWG pools have more of a problem of rising pH than non-SWG pools.

The two easiest ways to reduce the problem of rising pH, other than reducing the sources of aeration, are to lower the TA using Ben's Lowering Your Alkalinity procedure and using 50 ppm Borates (from Borax) if you have an SWG since that lets you lower SWG output since the Borates are an algaecide so do some of the work that chlorine would normally do. You can also not try and fight the rise as much and keep your pool at a somewhat higher pH.

Richard

[cnk]

So how much Borax would I need to add for a 12,500 gallon pool? Do I need to bring the PH down before or after adding the Borax? I tested my tap water & it has a PH of 7.2 so it's not naturally high.