Quote Originally Posted by CToon
Since I also suffer from the increase of ph syndrome , I've taken an interest in this ..I dont have the ph swings that some have reported , but I do need to add muriatic acid maybe every 10 days (varies , I havent kept track)

My pool
ph 7.5 normally
ALK 110
vinyl liner

Thinking of the possible cause/contributors , I wonder how much an effect DE is having behind the scene. I dont know the ph of diatomaceous earth , but since its a "chalk" , wouldnt it be alkaline ? and following that couldnt leaching be a contributor ?

just a thought
That's a possibility, but we'd have to see if there's a trend with the folks who see the consistent pH increase that isn't explained by other known factors like outgassing of carbon dioxide (which one can tell via the alkalinity drop over time, assuming pH is adjusted by adding acid). Are all of these people using DE filters?

Another possibility is the outgassing of chlorine gas, but this would not normally happen fast enough to affect pH except in salt pools -- either SWG pools or pools that have added salt. The concentration of salt (chloride ion) and the concentration of disinfecting chlorine (HOCl) determine the maximum rate of outgassing, though there are the same physical aeration issues as with carbon dioxide except that chlorine escapes more readily since there is virtually no chlorine in the air at all (so it's much further out of equilibrium) However, I don't have any evidence that this is really occurring in pools and it's very difficult to distinguish the difference between chlorine usage from breakdown by sunlight vs. outgassing except for the pH difference (the former is acidic, the latter is basic) and with so many things that can affect pH, well it's a mess to figure out!

You should also think about anything else added to the pool -- any other chemicals at all, including things to tie up metals and prevent staining. I know that non-chlorine shock (MPS) is very acidic, for example.

Then of course, there's the fact that people swim in the pool! I didn't think the pH of sweat was basic and I've seen reports of this rise in pH from people who don't use their pools much, so I don't think that's it.

At some point we may just give up on trying to explain this and just "live with it" and deal with it, but I'm not ready to quit yet!

Richard