daily pH increases

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rlsnights

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Sep 9, 2008
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Is it typical to have to adjust pH on a daily basis because it gets too high?

Our plaster pool was re-plastered about 3 years ago. I am testing the pH daily and adding acid at least 5 days out of 7. If I go 3 days without testing the pH is above 8.2.

This doesn't seem right.

And my TA never drops no matter how much acid I add to the pool. I've had the pH down to 7.2 for several days while fighting algae and my TA doesn't budge.

Any thoughts?

We keep our CC level on the high side to keep black algae in check.

Patricia

17,000 gal white plaster pool hayward pump and filter system jet-vac sweep
CC 8
pH 7.8 (going to drop it today)
TA 120
CH 260
CYA 45
 
That seems somewhat excessive, but there a couple of things that could be behind it.

First, a high chlorine level can make the pH read high. What test kit do you use?

Any aeration like a waterfall or fountain?

Adding acid alone won't lower your TA. You need to add enough to get the pH down around 7, and then aerate the water. Adding acid will drop the TA temporarily, but it will return to the same level as the pH rises.
 
First, a high chlorine level can make the pH read high. What test kit do you use?
FAS-DPD Taylor kit because I have to keep the TC on the high side.

Any aeration like a waterfall or fountain?
None and our pool doesn't get a lot of use - we have 2 teens and we do some swimming almost every day but it's usually only an hour or so.

Adding acid alone won't lower your TA. You need to add enough to get the pH down around 7, and then aerate the water. Adding acid will drop the TA temporarily, but it will return to the same level as the pH rises.

When I drop the pH the TA doesn't drop more than 10 pts - if that.

If I aerate to bring up the pH my TA goes up too.
 
Hey neighbor! :wave:

Daily acid additions is excessive, but not unheard of; especially with high TA. The acid should bring your TA down along with the pH. Have you tested your fill water? High TA fill water could explain why TA never seems to go down.

I hate to contradict a moderator, but my understanding is that acid brings down both pH and TA, and aeration raises pH without affecting TA. Thus, regular additions of acid will bring TA down regardless of whether you specifically aerate.
 
I have checked our regular water's TA before but did it again just now. It was the same as when I tested it before.

The TA of our regular water is 50 so that doesn't seem like it would be the cause. We only top off our pool maybe once every 2-3 weeks depending on how hot it is. If we have a streak of 100+ then we might have to add water every week.

I don't use liquid muriatic acid - we have a windy location and getting a face full of acid fumes once was plenty for me. I use dry acid instead.
 
anonapersona said:
Question for the experts -- if someone is using something OTHER than muriatic acid to lower pH, will it simply bounce back without affecting TA?
Click to expand...
No, all kinds of acid have the same effect on PH and TA as each other (assuming you use the correct amount). However, forms of acid other than muriatic acid add extra things that you may or may not want in the water. Dry acid adds sulfates, which are no problem in small or even medium amounts, but which can cause issues when their levels go very high.
 
Jason -

what constitutes a "high" level of sulfates? and how do I test for that?

Any ideas for me on how to keep my pH down?

Should I look at adding Borates? I haven't done that because I can't get the TA down much.
 
To stop the rapid rise of PH, you need to bring the TA down. Adding enough acid will do that, though it might take a while and lots of aeration to make it happen.

Sulfates are not normally tested for because they almost never get that high, but adding dry acid very frequently for a couple of years could do it.

By the by, I hope your CC level isn't actually 8? That would indicate a need to shock.
 
Just a note to say I have the same situation, so I'll be watching the thread with you! I have to add acid at least 3 times a week or it goes above 8 since I opened the pool in late May. My TA has gone down only 10 points with all the acid I've added this year--at least 8 gallons. ( I had new plaster a year ago May, but from what I read that cause of PH rise should be over by now. Had calcium scaling occur over winter from the high PH...)

TC 4.5 just about to add daily chlorine to bring it up to 7
CC.5
PH 7.8 (added acid 3 days ago down to 7.2)
TA 110 (started the summer at 120)
CYA 40
CH 240
 

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I'm not sure about rlsnights' situation, but Maria's situation might be that the acid addition is dissolving the scale which then has the pH and TA rise back up again. In fact, dissolving calcium carbonate scale or pool surfaces results in the TA rising even faster than the acid lowered it so you could end up at the same pH with the TA higher than before. This should slow down or stop once the scale is fully dissolved, though if the water were saturated with calcium carbonate you wouldn't be dissolving the scale in the first place.
 
That would be totally cool if I could dissolve all the scale by just tending the pH! It's just at the water line and onto the tiles, a bit further down on the wall, with much bigger granules that can be scraped off with a fingernail in the deep end. I would have NEVER known this--thanks so much for the insight!
Rlsnight, do you have any new roughness on your plaster? Did your pH rise a lot the first year and were you able to keep a lid on it? Were you able to keep the pH down when you closed the pool, if you did? Maybe we have the same explanation.....
 
Back from camping trip. Will try to reply to everyone. Darn Black algae trying to re-bloom while we were gone camping so pushing the TC up for a couple of days.

First - current levels

TC 10 (raising this again to TC 30)
CC 0 (made a mistake when I posted this as 8 earlier)
pH ? (was 7.5 before I started raising the TC to nip black algae again)
TA 120
CH 210 (started raising this today - goal 250+)
CYA 45

"Sulfates are not normally tested for because they almost never get that high, but adding dry acid very frequently for a couple of years could do it."

I have been using dry acid for about a year. Do you think I should try to check the sulfate level? How do I do that? Would it be affecting the pH and TA if it was really high?


"Rlsnight, do you have any new roughness on your plaster? Did your pH rise a lot the first year and were you able to keep a lid on it? Were you able to keep the pH down when you closed the pool, if you did? Maybe we have the same explanation....."

We have some scaling at the waterline but it's not much. I suppose that might be part of the reason for the rise in pH but I haven't noticed any change in the amount of scale. And my CH is on the low side which I think would mean that scaling would be less likely right?

We're in central California and haven't closed the pool in the winter. But that's something I'd like to ask about in a separate post.

Our pool was built in early 1960's and was re-plastered 3 years ago. I didn't handle the care of the pool after it was plastered - paid a guy that came highly recommended to do it for us cause I was up to my neck in taking care of a sick kid who was in and out of the hospital 7 times that year.

Back to the rising pH.

Is it possible for copper pipes to affect the pH and TA levels? I was talking to a friend about the pool and he asked about this. We have a combination of copper and pvc pipes.
 
No, copper pipes don't have any effect on the PH or TA. Though low PH could damage the pipes and put copper in your water.

Your rising PH is mostly because your TA level is 120. If you lower TA to around 70 or 80 the PH will be much more stable (though it may well still go up a little, but way less). There are instructions on lowering TA here.
 
I've lowered the pH to 7.0 or 7.2 repeatedly in the last several months. The lowest I've ever gotten the TA was 100. The pH pops right back up within a few days and so does the TA.

Do you think it's safe for me to drop the pH every time it comes up to 7.5 until I get the TA down to 70? I'm not sure how long that would take or how many times.
 
Hah. We are brushing the pool at least 2 x a day and often 3 when the black algae gets worse.

My fill water has a TA of 50.

Current levels

TC 10
CC 0
pH - last reading was 7.5
TA 110
CH 250
CYA 45

I'm bumping the TC up again. The TC at dusk last night was 30.
 
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