Rain & Ph

[DebbieO]

I'm thinkin' the rain upped my Ph. Am I crazy? Last weekend I was spot on with my numbers. Just ran a test (TF100) and here's what I got.

FC 7
CC 0
Ph 7.8
TA 90
CH 160
CYA 40

Went to the pool calculator to see how much acid to add and seen also that it was telling me to add baking soda, too. Won't the soda run up my Ph again? Should I just sit tight a minute & see if the Ph ticks down a bit on it's own? Have had a bunch of rain--had to pump water out 3 times in 2 weeks.

Thanks all!

 

[duraleigh]

pH of 7.8 is at the top end but acceptable. I would leave it alone until it goes to 8.0

What did you want to lower it to?

Baking soda has no measurable affect on your pH but you don't need any, either.

Last, the rain has very little affect on your pH but if it's enough rain and it's far enough away from your pool pH, it could move it a point or two, I suppose.

A "normal" rain is typically a non-event to a pool although many people seem to think the results will be drastic.

 

[alanpaul]

DebO,

Here in South Florida, we get 5 feet of rain per year, averaging 5-10 inches per month (because we have a dry season in the winter). This week we've had over 6 inches already, and we're forecast to have as much as 5-10 inches in the coming week.

And the answer to your question, specifically in our environment, is: Yes. When we get a lot of rain, we usually have to add acid to re-balance the pH. Only once in quite a few years do I remember having to raise the pH after a lot of rain.

Someone once told me that here on the peninsula of Florida, the pH of the rain is affected differently depending on whether it is a storm from the Gulf of Mexico - west, or a storm from the Atlantic Ocean - east. I'm not certain I believe that theory.
Alan

 

[duraleigh]

we usually have to add acid to re-balance the pH

How many points would you say your pH raises after a big rain?

 

[DebbieO]

I wanted to bump it down to 7.4 or so. Since I joined this site I have become compulsive! We did have a couple major downpours. The kind that make you pull off the road when driving.

So, thanks for the quick answers. Guess I'll go net the cottons instead!

 

[alanpaul]

@ Dave S. Duraleigh,
FYI, It 's not been unusual for our pH of 7.4 or 7.5 to rise anywhere up to 8.0 as it did just this week after more than 4 inches of rain within 36 hours.
Alan

 

[duraleigh]

Most pools have an average depth of about 48" or so. A 4" rain would possibly replace a bit less than 10% of the pool water.

So, it seems to me that rain would have to have a pH up in the teens (I think) to have that kind of influence on the remaining 90% of the 7.4 water??

I wonder if that SWG was a big contributor somehow.....it just doesn't make sense that rain can be that high.

 

[alanpaul]

@ duraleigh
Yes, it's a puzzle. 4" of rain equates only to an additional 7.4% of water in our pool, and shouldn't have that effect, but often it does.

I suspect that run-off from the shingle roof and concrete deck (though it mostly drains away from the pool) have some effect as well.

Our SWG, listed as dead in the signature, is currently non-functional. I'm expecting the replacement Current Limiter to arrive in today's mail. :-D
Alan

 

[tmnt25]

I concur with Alan, it's been raining pretty hard the last couple days and my ph keeps climbing after adding muriatic.

 

[linen]

As duraleigh pointed out, the ph of the rain itself (usually it is acidic with low TA, netting little effect) does not change pool ph much.

Rains like you are having can cause significant aeration, which of course raises ph.

 

[Patrick_B]

I have to agree with Dave an Linen here. And remember moving the pH one whole point say from 7.0 to 8.0 is a really HUGE change.

The pH scale is a log of ten, so a pH of 7.0 is TEN TIMES more acid than pH 8.0.

Unless rain is washing a lot of something into the pool, I don't see how even a good rain would change pH much at all.