Rapid CHanges in pH

[scgms1]

We built this pool in 2003, so I've had 15 years of experience with this. I've noticed over the years that the pH has been very consistent, usually in the 7.6 range. Acid was something I have on hand, but only small amounts were needed. Something has changed recently and I'm askingfor advice.

6/9/18 Test Results

FAC - 3
TAC - 3
CH - 350
CYA - 60
pH - 8 Where exactly it is, I'm not sure as that's as high as I can see using Leslie's 81329 test kit
TA - 200

I'm out of acid so I run down to a local pool supply company and pick up 4gallons.

I add 1/2 gallon and I'm at checking it the next day-

pH 8
TA 200

I add 1 gallon and the following day-

pH 7.8
TA 160

4 days later I test it again and the pH is back up

pH 8
TA 140

I call the pool supply place and ask about the MA. It looked fresh in brand new bottles and crates, but I don't know. Nope, we haven't had any problems. I go to Leslie's and pick up 2 gallons of MA.

Multiple tests later and a total of 5 gallons of MA I get -

pH 7.4
TA 110

I think I finally got this until I checked the water 4 days later

pH 8
TA 120

I dumped another gallon in yesterday and here are my results this morning -

FAC 6
TAC 6
CH 340
CYA 70
pH 7.4
TA 120

I've been using Bleach and had put some in to get the FAC & TAC up. We hadn't used tablets for a while, but I recently put some in.

Any ideas on what to look for? I'm at a loss here and have been lax on checking the pH & TA, only because it has been stable for many years. This seems to defy science...Thank you

 

[Dirk]

Re: Rapid Changes In pH

Things to check:

- the expiration date of your testing ingredients. They can go bad over time. Perhaps buy a fresh set of reagents just to verify that is not the problem. You'll need them eventually if not.

- the strength of the acid vs the strength you've used in the past. Freshness is one thing, sometimes vendors switch strengths, 31% down to 14% is not unheard of. My Lowe's carries 14% only. Other Lowe's carry the 31%. You have to check each time you purchase, and adjust your dosing habits accordingly.

- the pH of your fill water. My city alternates water sources throughout the year, based on availability. Each source has a different chemical composition, including different pH. It's prudent to test your fill water periodically, so you can monitor changes that can cause the problem you're experiencing. If you keep a record of your fill water levels, then you can use that data to understand better what's going on when things like this occur. Maybe too late for this time around, but something to do moving forward. If your fill water has higher pH than it used to, that might be all this is.

- tablets which contain CYA can greatly affect your pH, though perhaps not in the direction you're experiencing based on when you used them. Just something to be aware of as you troubleshoot this.

- aeration causes pH to rise. Have you added any water features? Running a waterfall more than you did? Did you adjust your returns so that they are rippling the surfaces more than they did? Anything new causing bubbles in your pool? Kids doing lots of diving and cannonballs that didn't before?


Others here will hopefully have other possible causes...

 

[JamesW]

Re: Rapid Changes In pH

Do you have an autofill?

The high TA at 200 is the issue. I suspect that it might be high due to high TA fill water and maybe a leak where an auto fill is running to keep up.

What is the normal TA?

Any chance that baking soda was added?

Any other chemicals added?

Borates added?

 

[scgms1]

Re: Rapid Changes In pH

Thanks Dirk,

I should have mentioned this but I forgot. I brought samples in to the pool supply place and also to Leslie's. Their readings were not exact, but were close to mine. The guy at the pool supply place said he's experienced this before when I questioned him about the acid. His reply was to keeping adding it until it "breaks," what ever that means.

The pool supply place didn't have the concentration listed on the bottles. They come in orange containers. Leslie's has 31.xx% listed on theirs.

I checked the tap water and it also read 8 on the pH. I don't know if it's 8.1, 8.2, 8.6...

We haven't turned on any of the water features lately and the pool hasn't been used that much this year.

Thank you

 

[scgms1]

Re: Rapid Changes In pH

Yes, we do have an autofill. Good question, maybe turn this off and see how quickly the water drops? Possible leak? The temperatures have been in the high 80's - low 90's, what would be the normal evaporation rate? The pool is exposed to the sun from 10 AM to about 4:30 PM. Water temperature is about 82* F.

TA has been in the 140 range, but because the pH has been normal I hadn't done anything to get this lower.

I have only added bleach and the past 2 weeks I had put some tablets in. No baking soda, borates, or any other chemicals.

Thank you

 

[JamesW]

Re: Rapid Changes In pH

What is the TA of the fill water.

Something is raising the TA.

Is the CYA dropping recently?

If you have a leak and an autofill is adding water, the CYA will drop and the TA will begin to go towards the TA level of the fill water.

 

[mknauss]

Re: Rapid Changes In pH

what would be the normal evaporation rate?

This time of year it would be of no surprise if you are losing 3/4" to 1" of water per day due to evaporation.

 

[Richard320]

Re: Rapid Changes In pH

If the acid is HASA stuff, 4 used-to-be-pink-but-now-faded returnable jugs to an orange crate, it's 31.45% acid.

 

[scgms1]

Re: Rapid Changes In pH

This time of year it would be of no surprise if you are losing 3/4" to 1" of water per day due to evaporation.

It would have been helpful to know what was normal before I ran into a problem. I should have looked at the water usage prior to this to know what is normal. I received my last water bill and it didn't jump dramatically. I'll look over some previous water bills to get an idea.

- - - Updated - - -

I'll have to check the TAC of the fill water tonight when I get home.

The CYA went up from 60 to 70, which I thought was odd after only adding 5 tablets. Maybe I read it wrong, but either way it didn't seem to drop.

 

[Arizonarob]

Re: Rapid Changes In pH

You can do a simple test to see if your pool is leaking, or just evaporating. Get a 5 gallon bucket and place it on the second stair of your pool. Fill the bucket with water so it as the same level as the pool water. With the autofill off, at the end of the day check the level in the bucket. If the water in the bucket is the same height as the pool water, no leak. If it’s more then the pool, then you have a leak.

 

[scgms1]

Re: Rapid Changes In pH

You can do a simple test to see if your pool is leaking, or just evaporating. Get a 5 gallon bucket and place it on the second stair of your pool. Fill the bucket with water so it as the same level as the pool water. With the autofill off, at the end of the day check the level in the bucket. If the water in the bucket is the same height as the pool water, no leak. If it’s more then the pool, then you have a leak.

That's a great idea! Thank you!

 

[scgms1]

Re: Rapid Changes In pH

What is the TA of the fill water.

Something is raising the TA.

Is the CYA dropping recently?

If you have a leak and an autofill is adding water, the CYA will drop and the TA will begin to go towards the TA level of the fill water.

That was a good thought James. I'm not sure how rapidly things change with the fill water, but this means that might not be the problem.

Fill water -

pH 8
TA 60

The pool water when I tested again this evening when I got home -

pH 7.4
TA 110

I don't know at this point, I wonder if someone is messing with me...That makes no sense, but this is strange.

 

[mknauss]

Re: Rapid Changes In pH

You said in your first post you had added some tablets. What are they? Especially any additional ingredients beyond Trichlor.

 

[JamesW]

Re: Rapid Changes In pH

Very odd. If the TA really was 200, something had to be added that was basic.

 

[scgms1]

Re: Rapid Changes In pH

Very odd. If the TA really was 200, something had to be added that was basic.

The TA was at 200 when I started with this. As I mentioned I've been lax testing for pH & TA because this has been stable for 15 years. I do check it, but not at the same frequency as I'm checking the chlorine levels. What got me started on this was I noticed white deposits on the side of the pool. We have flagstone tiles.

I had to make a trip to pick up MA and stopped at Leslie's & the pool supply company with water samples. They both came back with 8.0 pH and I looked on the sheet that Leslie's gave me - 190 TA, and the pool store had 210 TA.

I turned off the water to the auto fill this morning and put a graduated painters bucket (5 gallons) and measured it exactly. I'll see what the evaporation rate is. If the TA on my water supply is 60 I don't think I'm dealing with a leak, but I had checked the water in the kitchen. I'll let the water drop in the pool and take a sample directly from the autofill. I would imagine it should be the same as we have copper pipes and the autofill is hooked to an outside line that we ran PVC pipe to the autofill. It seems unlikely that there's something unique to that line, but I'll eliminate that possibility.

Short of that, I think I'll pick up some cameras this weekend. Something strange is going on. Everything has an explanation, I just don't have an answer to this yet. Thanks for the help!

 

[scgms1]

Well, I think I've come up with a solution - go to a equipment rental company and rent a backhoe...

Seriously - I thought this was under control, but this morning (7/1) I checked and the pH was back at 8. The TA was 110..

6/29 the pH was 7.6. I didn't check yesterday.

The pool doesn't have a leak using the bucket method and after 3 days the evaporation was right about 1/2". I checked the pool fill water directly and it matched what I got from the house - 8 pH and TA 60.

One thing I didn't have in my signature is we have a Pentair MiniMax NT pool heater. Is this a possible cause? I can't think this would do anything. The pool equipment was swapped out 2 years ago and we went from DE to a cartridge filter and changed the main pump to a VS pump. This should not have affected the pH, right?

The tablets I added (which I stopped, were picked up from Costco - Clorox XTRA Blue) The ingredients listed Trichloro-s-triazinetrione 94.05%, Other ingredients 5.95%.

Short of renting a backhoe, what else can I do, or look for?

 

[mknauss]

The tablets would have suppressed the pH and kept the TA down. I do not recall if you were using tablets and then changed to liquid chlorine when this pH/TA issue arose.

Those tablets add copper. Do not use them.

None of your equipment would have an effect on your TA and pH.

 

[jbarn]

Good call on the TA

 

[scgms1]

The tablets would have suppressed the pH and kept the TA down. I do not recall if you were using tablets and then changed to liquid chlorine when this pH/TA issue arose.

Those tablets add copper. Do not use them.

None of your equipment would have an effect on your TA and pH.

Good morning,

Duly noted on the tablets and I stopped using them. I haven't used tablets for over a year and recently started using them after the problems with the pH and TA. Not because of the problems, but I had some lying around. For the past year, the only thing I have put in the pool is bleach.

I'm getting a little frustrated, not with you, or anyone else, but trying to figure out what is going on here.

For 15 years this pool might have used 10 gallons of MA, now in the last month I'm up to 7 gallons.

I know you guys don't recommend pool water testing by the pool supply companies, but I went yesterday to Leslie's again with a water sample. pH 8 TA 110. You need some acid - I've put 6 gallons in the past 3 weeks, going on a month now. Do you remember me? Yes, but it needs acid. I'm back to, in 15 years this pool might have needed 10 gallons total. They test for salt and they have an Ah - Ha moment, there's the problem the salt level is 2,300 PPM. He says that happens when using liquid chlorine. I'm not a chemist, but I'm not sure what has to happen to produce NaCl from liquid chlorine. It seems more likely to have occurred from swimming and sweat, not liquid chlorine. We're at year 7, or 8 from when the pool was drained the last time.

I see no mention of testing for that here, and I can't imagine people with SWG's needing that much acid.

Something in this pool has turned into a "base" generator. We've eliminated some possibilities - the fill water for the autofill and the pool equipment. That leaves - ??

 

[Demegrad9]

Yes using bleach does increase Salt, just check out 'Pool Math', for me each gallon of 12.5% bleach raises FC 4ppm and Salt 6.6ppm. But who cares? All forms of chlorine are going to increase salt, again play around with the 'Effects of adding chemicals' section of 'Pool Math'. And people with SWG pools intentionally maintain more salt in their pools, more like 3,500ppm, and they don't have such issues with pH/Ta. So anyway, sorry that's not the issue here.