We just had storms move through here this morning, we had 2.75 inches in the rain gauge.
I tested the PH and FC.

Ph 8.2 very purple
FC 6.5

Yesterday it was

Ph 7.5
FC 6

I guess its the rain that raised the PH, will this come down on its own or do I need to add some MA?

Thanks

We received about an 1.25 inches this morning and my Ph did not rise at all. It stayed right around 7.4 from the day before. Did you run your pump after the storm? I would make sure you run it, test again and then if it is still high I would add MA. BTW I didn't need to add any after the last big storm on 1/9 either. During that storm we had over 7 inches of rain.

Confirm your test results because rain should not have that much affect on pH. Nevertheless, if your pH is higher than 7.8, bring it down with muriatic acid. It will not come down on it's own.

duraleigh I retested and same results, I had started the pump as mentioned by Flippy so I just added the MA.

I'm confused as I use a pool log that I got from Bama. I record my reading daily as I'm still learning.
What could have made it go that high?

Must be the BS content in those Texas rains...

Sorry, being from NM I couldn't resist!

Well, Pool monitor's idea may have merit ( ) but probably the most important thing is not to worry too much about what caused it.

What's really important is that you tested and found the issue and know how to correct it. Bring it back on down and keep an eye on it...rain or not.

Ok, thanks again.

There's no way to tell without ALL the readings, but I will hazard a guess. You probably have high TA. Heavy rains - the kind that make it look like the pool is boiling - aerate it, which drives up the pH. As a consolation prize, the TA should be lower than it was.

When I test after a good rain, I like to let the pump run at least an hour and do a good brushing with the wall whale to be sure the water is well-mixed.

Thanks Richard. I have the pump running now after adding the MA. I don't do a daily test of the other reading but as it has started to rain again here I'll run a complete test tomorrow and report back. My last complete test on 1/16/2012 was:

Ph 7.5
FC 6.5
TA 60
CH 120
CYA 30
Bor 50
Temp 54

A hard rain always drives my PH up .2 or .3
I always add some extra bleach if I have a chance if I know it's coming too.

I had the same happen here. Bucketing down for days. The overflow couldn't even keep up in the end so water was pouring over the side. While it was raining I googled the pH of rain water to guess the effect on the pool when it eventually stopped. Average rainwater pH seems to be 5 to 5.6 so I thought in theory it should come down a little if anything. When it stopped raining and I did my test and the pH has gone up from 7.5 to 7.9.

When I thought it through I came to the exact same conclusion as Richard that the heavy rain had aerated the pool which caused the pH to rise. As Richard also suggested, my TA had gone down by about 20ppm. I assume that's just dilution. Shame because I just added calcium and cya the day before the rain started... I assume they will have been diluted down too.