How often should I realistically have to add acid?

[No4Mk1]

I have a plaster ig pool we built last summer. Things are starting to warm up here in Houston, so I've been watching the chemicals more closely and we have even heated it a few days to let the kids enjoy it during spring break.

Since we put the pool in it seems like it has required constant feeding of muratic acid. I'm not sure if this is normal or not, but it seems odd to me. I seem to add 1/2 - 1 gallon of muratic acid per week now that things are warming up. I know my TA is a little high, is that what is causing this?

Here are all my levels taken earlier today... what do you think?

TC/FC 5
pH 7.8-8.0 (I can never really differentiate these two welll)
TA 125
CH 275
CYA 85

 

[JasonLion]

As plaster cures it raises the PH. This happens quickly for the first three or four weeks, and then more slowly for up to a year. It sounds like you are still in your first year, so part of the PH rise is going to be from the plaster.

High TA levels can also cause the PH to rise, especially if you have a source of aeration, like a negative edge, SWG, waterfall, scupper, spill over, fountain, etc. Lowering your TA, or allowing it to go down on it's own, will reduce the rate at which PH goes up. The more aeration you have, the more important it is to lower your TA.

 

[No4Mk1]

That all makes sense. We do have a spill over from the spa to the pool so that is probably doing it. Thanks for clearing that up for me!

 

[PoolGuyNJ]

While the alk is a bit high, remember that CYA will cause it to read higher than it effectively is.

You pH appears a bit on the high side though. If you have a salt cell, I suggest bringing it down to about 7.5/.6 or you may get some scaling. Salt cells tend to cause pH to rise also. Being in Texas, your plaster tends to cure somewhat faster than here in NJ due to the higher mean water temp over the course of a year.

Scott

 

[Sportsman]

I'd test the pH and TA of your fill water too. Our fill water is high in both and in the summer when I'm adding lot's of water to counter evaporation I probably added a half gallon of acid per week though it slowed as I got my TA down in the pool.