pH question

[waterbear]

Yes, having your solar blanket on most of the time will virtually eliminate carbon dioxide outgassing which is usually the main cause for rising pH (so having your cover on will virtually "freeze" your pH).
Richard, I have not found this to be true. In the colder months I keep a solar cover on my pool and spa and still have to add acid just about as freqently as when it is off. I will see if the borates make a difference this winter. I usually have to put them on around november.

Would appreciate your comments!

[chem geek]

Evan (waterbear),

Well every pool is different, but a cover should have really kept your pH much more stable. My own pool that is usually covered hardly changes pH at all now that I only use liquid chlorine, though it obviously dropped in pH and needed regular base addition when I used to use Tri-Chlor tablets.

Most of the users that report a sudden stop in their pH rise have reported using a pool cover at the time of this "freeze" in pH, so I don't know why you don't see the same thing. The borates should slow down the pH rise, but when you do eventually need to add acid, you'll have to add as much as you did before because the borates will make it just as hard to lower the pH (by adding acid) as they make it hard for it to rise. Of course, report back when this occurs and prove me wrong!

If you find that your rise in pH over time is not accompanied by a slow drop in TA, then there is some source of pure base in your system. I forgot -- is your pool plaster/gunite and when was it last redone? The curing of the cement in plaster/gunite will raise the pH and will also raise the CH though this may not be as measurable as pH. A pool cover won't do anything for this source of pH rise. Also, if you add any chemical to your pool during winter, such as a polyquat algaecide, then perhaps this is basic, though I do not know (I thought polyquat was relatively neutral).

Richard

[waterbear]

My pool is fiberglass (which I assume is non reactive) and I live in Florida so the pool is open year round. I do turn the output on my SWG down in the colder weather and shorthen the pump run time a few hours but I still had the pH rise. My alk stays pretty constant....might be from my fill water which has a TA of about 110 ppm. The only alkaline substance that goes into my pool on a regular basis is the sodium hypochlorite produced by the SWG.