Constant excessive PH rise - Plaster Pool

[gokart]

Saltwater pool
30,000 gallons
elevated hottub approx 1500 gallons??
Built Spring 2019 (6th year)
Mid dark plaster

Basic problem: PH keeps rising even when water is not circulating.
Did a test yesterday, PH around 5PM was 6.8. This morning at 5AM the PH was 7.2. The pump was not running.

Last year when I closed this pool, the PH was 6.2 (deliberately) when I closed it, and 7 days later I peeled the cover back and took a reading at above 8. I'm using the drops to test this. Below is my water test from Yesterday. (I can post my water tests from the pool open if it would help).

Latest Tests:
FC: 3.6
TC: 3.64
Combined Chlorine: 0.04
PH 6.8
Alkalinity 79 PPM
Adjusted Alkalinity 72PPM
Calcium Hardness 364 PPM
CYA 25
Iron 0
copper 0.10
PHosphate 1721 PPB (spring around here, can you tell?)
Salt: 3.227PPM
Temp 80
Calculated CSI -0.88

I've had white build up on the dark plaster for a number of years. Last year the pool guys came out and used three gallons of Muriatic acid in the hottub to remove the sharp crystals and white stuff that built up over winter. (The pool has had this build up over winter the past 4 years, it's just getting worse).

This year, when I opened the pool, I expected the hottub to be destroyed, but also found for the first year this happened, the crystals growing on the main pool itself instead of just having a white powder at the bottom of the pool. There were even crystals growing on the black rubber innertube that I had in the hottub to keep the cover elevated for rain water run-off.

What could be causing this constant PH rise?

Yes it's a salt water pool. Right now the Salt control head exploded due to ants and isn't even connected (it's in my garage on my workbench). The ozone system has also been disconnected after I read many comments on these forums about it not being needed. (Immediately saw a reduction in chlorine demand, imagine that). This year I have NOT been running the water feature much at all, except to exchange the water in the hottub once per day. I'm still seeing massive PH rise even with the salt and ozone systems disabled and no visible aeration when circulating the main pool. Runtimes are approximately 4 hours per day at this time of year.

 

[Bperry]

Saltwater pool
30,000 gallons
elevated hottub approx 1500 gallons??
Built Spring 2019 (6th year)
Mid dark plaster

Basic problem: PH keeps rising even when water is not circulating.
Did a test yesterday, PH around 5PM was 6.8. This morning at 5AM the PH was 7.2. The pump was not running.

Last year when I closed this pool, the PH was 6.2 (deliberately) when I closed it, and 7 days later I peeled the cover back and took a reading at above 8. I'm using the drops to test this. Below is my water test from Yesterday. (I can post my water tests from the pool open if it would help).

Latest Tests:
FC: 3.6
TC: 3.64
Combined Chlorine: 0.04
PH 6.8
Alkalinity 79 PPM
Adjusted Alkalinity 72PPM
Calcium Hardness 364 PPM
CYA 25
Iron 0
copper 0.10
PHosphate 1721 PPB (spring around here, can you tell?)
Salt: 3.227PPM
Temp 80
Calculated CSI -0.88

I've had white build up on the dark plaster for a number of years. Last year the pool guys came out and used three gallons of Muriatic acid in the hottub to remove the sharp crystals and white stuff that built up over winter. (The pool has had this build up over winter the past 4 years, it's just getting worse).

This year, when I opened the pool, I expected the hottub to be destroyed, but also found for the first year this happened, the crystals growing on the main pool itself instead of just having a white powder at the bottom of the pool. There were even crystals growing on the black rubber innertube that I had in the hottub to keep the cover elevated for rain water run-off.

What could be causing this constant PH rise?

Yes it's a salt water pool. Right now the Salt control head exploded due to ants and isn't even connected (it's in my garage on my workbench). The ozone system has also been disconnected after I read many comments on these forums about it not being needed. (Immediately saw a reduction in chlorine demand, imagine that). This year I have NOT been runnView attachment 569786ing the water feature much at all, except to exchange the water in the hottub once per day. I'm still seeing massive PH rise even with the salt and ozone systems disabled and no visible aeration when circulating the main pool. Runtimes are approximately 4 hours per day at this time of year.

Welcome!

Its gonna sound obnoxious but not meant to be but those kinda of problems seem common with owners who trust pool store testing and advice. The pool store testing has been shown to be terribly innaccurate and hence leads to bad/dangerous advice. Your pH is rising fast likely because they have you keeping it too low and advising you to keep your TA too high. Elevated TA makes the pH rise faster and very low pH also contributes to faster pH rise.

Take a look through the pool school articles and id be remiss if I didnt advice you to get one of the two TFP recommended test kits to do your own testing.

Swimming Pool Test Kits Compared

What pool test kit should I buy? Why not use test strips? Our recommended test kits will pay for themselves in no time!

www.troublefreepool.com

 

[gokart]

I guess I don't totally understand. Pool math app shows TA should be between 50 - 90. It's 79. The test before that showed 100 TA and I've used about 6 bottles of MA this week. So I'm actually buying 79 as a decent result. (I will look into test kits as well though)

So if low PH causes fast PH rise, what should I really be doing here when the PH gets to 8+ like it did just the other day? I'm so not understanding this. I honestly believe it was a bad plaster job, but the Pool company says there is no warranty because of my inability to keep the pool chemistry in check. They also refuse to help even answer any very basic questions.

 

[Jimrahbe]

Go,

pH is a funny thing.. I have three saltwater pools in the DFW area.. All three pools have the same equipment, are about the same size, with no water features.

Two of them have what I consider a normal pH increase.. I have to add about 30 oz. of MA about one a week or so. The other pool, has a very slow pH increase and I can often go a month or more between acid doses.

I think a lot has to do with the local water.. What is the TA of your local water??

All three pools have a TA of between 50 and 60 ppm. This makes a lot of difference for me.

Most salt water pools like their pH to be about 7.8. So, dropping the pH to 7.2, just makes it try to get back to 7.8 faster. I only drop it to 7.5 or so..

A gallon of MA will drop your pH by 1.0.. So if you have 8.0 it will drop it to 7.0. You are just making this hard on yourself doing this.

Thanks,

Jim R.

 

[Bperry]

I guess I don't totally understand. Pool math app shows TA should be between 50 - 90. It's 79. The test before that showed 100 TA and I've used about 6 bottles of MA this week. So I'm actually buying 79 as a decent result. (I will look into test kits as well though)

So if low PH causes fast PH rise, what should I really be doing here when the PH gets to 8+ like it did just the other day? I'm so not understanding this. I honestly believe it was a bad plaster job, but the Pool company says there is no warranty because of my inability to keep the pool chemistry in check. They also refuse to help even answer any very basic questions.

There’s a good chance that the store testing your using is not very good at it and your TA actually isn’t 79. pH is a weird thing. Mine has been 7.9 for about two months now and I haven’t added acid since I opened the pool and I had it replastered right before winter. It unintuitive in that the farther you push the PH away from its natural happy place the faster it will change to get back to that. Try leaving it at 7.8 until your TA gets down to 50. But dont continue to let the pool store do your water testing As all kinds of goofy things start to happen when people do that. You may be experiencing that as well.

 

[gokart]

Ok I'll get a TA kit, however let's just assume for a bit the numbers are correct, What's causing the scale then, not the high PH that occurs over the winter or something else about the water chemistry? (not enough/too much TA, not enough/too much calcium? ) The orenda calculator suggests that I'm currently in the right range - and I'm seeing a lot of "dust" when brushing the pool and the filter is requiring backwash very frequently, I suspect the calcium buildup (aka calcium silicate) is starting to return to suspension and come off the plaster.

The ultimate goal here is to keep this scale/buildup/whatever you want to call it from happening in the first place.

 

[Bperry]

Ok I'll get a TA kit, however let's just assume for a bit the numbers are correct, What's causing the scale then, not the high PH that occurs over the winter or something else about the water chemistry? (not enough/too much TA, not enough/too much calcium? ) The orenda calculator suggests that I'm currently in the right range - and I'm seeing a lot of "dust" when brushing the pool and the filter is requiring backwash very frequently, I suspect the calcium buildup (aka calcium silicate) is starting to return to suspension and come off the plaster.

The ultimate goal here is to keep this scale/buildup/whatever you want to call it from happening in the first place.

View attachment 570286

A positive CSI (LSI is similar but not the same) is what contributes to scale. But if the test results are not accurate you dont know whats going on. Innaccurate results are worse than nothing.