Adjusting pH

[PeterQ]

Hello,
Here are my test results for today.
pH 8.0 (btwn 7.8 and 8.2)
FC 6.5
CC 0.5
TA 90
CH 275
CYA 70

The pH has trended up from 7.2 to 8ish over the last 5 weeks. I think that means I need to add some muriatic acid, correct? What should I target for pH? I was thinking 7.5 but in reading posts on the forum, I've seen Richard mention targeting 7.2 in a few places to help eliminate calcium scaling. I have no idea if scaling is a problem at this point in my pool. I'm also told I probably only have a 3-5 years left before it needs to be resurfaced so I'm not all that worried at this point about a little scaling. (The pool is new to me this year.)

Thanks in advance for any help.
Peter

 

[steveg_nh]

I would target PH of around 7.4. That may it gives you some breathing room before you treat again. I like ph around 7.5-7.6. And yes, MA is ideal in most cases, especially if you have a SWG. But you are plaster, so I'm not 100% sure. Careful with hit though, if you haven't used it before. Did you read up on PH in pool school? It will tell you everything you need to know...great info in there.

 

[PeterQ]

I have read Pool School, pretty much every word. It talks about target ranges and how to adjust, but doesn't discuss when you are adjusting, where to target. Seeing as the level has been slowly trending up, I'm guessing aiming for the low end of the range is ideal. I have also seen mention of 7.2 as a target, so just trying to get a sense of what my ideal target should be.

 

[JVTrain]

Plug in all those test results into Pool Math. If you're concerned about scaling and your plaster, once you have all the numbers in the Now column, look at the CSI number toward the bottom. With your numbers plugged in, I have a current CSI of 0.31 which means some potential for scaling. If you put in a pH of 7.4 in the Target column, the CSI is then -0.24 which is balanced, not quite corrosive to plaster. If you change the Target pH to 7.2 the CSI changes to -0.42, potential to be corrosive to plaster. Anything 0.6 or greater for CSI will cause scaling, anything less than -0.6 will cause corrosion. It's a grey possibility area at > 0.4 and < -0.4.

Tinkering with Pool Math is very helpful and dare I say it... FUN!

 

[mrcarcrazy]

Plug in all those test results into Pool Math. If you're concerned about scaling and your plaster, once you have all the numbers in the Now column, look at the CSI number toward the bottom. With your numbers plugged in, I have a current CSI of 0.31 which means some potential for scaling. If you put in a pH of 7.4 in the Target column, the CSI is then -0.24 which is balanced, not quite corrosive to plaster. If you change the Target pH to 7.2 the CSI changes to -0.42, potential to be corrosive to plaster. Anything 0.6 or greater for CSI will cause scaling, anything less than -0.6 will cause corrosion. It's a grey possibility area at > 0.4 and < -0.4.

Tinkering with Pool Math is very helpful and dare I say it... FUN!

At least I'm not the only one that finds it entertaining to play with.

 

[JVTrain]

At least I'm not the only one that finds it entertaining to play with.

Haha. We're both in the club.

Also seriously... the grey area for potential scaling and corrosion is actually > 0.3 and < -0.3 Apparently I'm a nerd who can type faster than my brain can think.