Fast rising PH in SWG pool

[zemurray]

Hi,
New pool owner here. I've been lurking and learning for a bit. My wife and I have a 20k gallon fiberglass pool that has been open for a month now, learning about water chemistry, using drop tests, etc..

What I've noticed is a pattern of rapid rising PH, where I'm having to add a gallon or 1.5 gallon of 31.5% muriatic acid a week. Weather has been mostly sunny, not very much rain over the last month. PH seems to rise .3 per day on average. If I knock it down to 7.3 or 7.4, it will be back up to 8 in 3 days. I'll add 64 oz of acid, get it back down to 7.3 and repeat. Adding baking soda 3lb at a time to compensate for acid. I have tried playing with TA a bit to see if it has an effect on the rate of rise, it doesnt really. I tried TA of around 80 to 100 and it doesnt make a material difference.. I have been testing PH and Chlorine daily with TF pro kit. The other parameters weekly. I've done quite a bit of reading and searching on this, and was nearly resigned to it being normal for a SWG pool, but it still seems excessive. I noticed some SWG owners rarely add acid? I've looked into borates as an additional buffer, but I'm not sure if I want to go that route at this time.

Imagine Fiberglass pool, 20k gallons.
Pentair SWG
Cartridge filter
No water features.
Pump running 40 gpm full time.
heated at 84F.

PH = 7.8 (today) maintained between 7.3 to 7.8 (got to 8.1 while I was out of town for 3 days).
TA = 80 (today) maintained between 80-100.
FC = 2-3
CC = 0
CYA = 50
CH = 150
Salt = 4020
Water Temp = 84F

No borates.

For reference, Imagine pools requires me to log test results and maintaining their recommended values (below) for keeping the warranty valid.
PH 7.2-7.6
Total Alkalinity 80-120 ppm
Calcium Hardness CH 150-200ppm (for fiberglass, manual states to never add any)
Free Chlorine 1-2ppm - max 5ppm
Combined Chlorine - 0
CYA 30-50ppm

 

[PoolStored]

Your warranty requirements are at odds with nature.

With a TA of 80, your pool likely will be fairly stable with a pH of 7.8-8.0.

High TA and low pH cause pH rise. When you force pH down to 7.3, 7.4, it will naturally want to rise. SWCG is pH neutral.

I would not force it down to 7.3, 7.4. Just lower to 7.6 to maintain warranty.

PH TA Relationship - Further Reading

www.troublefreepool.com

 

[zemurray]

Some of the reading seemed to suggest that SWG has an aeration effect, although my SWG is set to run 8% and holding FC steady.

So what TA would be required to keep a stable PH of 7.6 ? Should I call the manufacturer and discuss the values they are suggesting?

 

[PoolStored]

So what TA would be required to keep a stable PH of 7.6 ? Should I call the manufacturer and discuss the values they are suggesting?

Don't know, every pool is different. 50,60,70 might be sufficient.
Can't advise on the Manufacturer...they are going to say what they are going to say...

 

[pjt]

PH 7.2-7.6
Total Alkalinity 80-120 ppm

That's an impossible task. You'll never win that battle, as you're finding out.

I'll add 64 oz of acid, get it back down to 7.3 and repeat. Adding baking soda 3lb at a time to compensate for acid.

You're on the MA / baking soda seesaw. You'll perpetually add MA, then baking soda, then MA, then baking soda, etc.. Most SWCG pools eventually reach equilibrium with a TA ~60 and pH in the high 7s (both of which are perfectly fine).

 

[reggiehammond]

My pool pH won't stabilize until TA is 50-60. 60 or higher, no way.

 

[zemurray]

Thanks for the replies everyone. This helps my understanding quite a bit. I'll target a lower TA and work with my dealer/manufacture to see if they will give me something in writing to prevent a warranty issue.

 

[sande005]

Here's from their warranty:

15. failure to maintain a monthly written record of the water levels, including the levels of chlorine, free chlorine, pH, total alkalinity and calcium hardness (with calcium hardness to be tested by a pool shop at least every 6 months);
16. failure to maintain the pH level of the water between 7.2 and 7.4, the total alkalinity level between 80 to 120 parts per million, the calcium level between 80 and 120 parts per million (for claims under a Product’s surface limited warranty), and/or the free chlorine level between 1 and 3 parts per million;

Yikes - a lifetime written monthly record for the shell warranty, a 10 year record for the gelcoat. I didn't go deeper in it, but there probably will be an abrasion exclusion, due to the constant scrubbing of algae.....

 

[reggiehammond]

Thanks for the replies everyone. This helps my understanding quite a bit. I'll target a lower TA and work with my dealer/manufacture to see if they will give me something in writing to prevent a warranty issue.

They're not interested in providing a warranty, nor are they concerned with the actual quality of your water.
I'd really recommend just ignoring their warranty and requirements and focus on taking care of your pool with TFP methods.

If you follow their requirements, you'll have frequent algae due to insufficient FC. You're already at or below FC levels today.
FC/CYA Levels

 

[sande005]

Besides - if it fails, their maximum liability is the wholesale amount the dealer paid to them. Not your cost to remove and replace (if it comes to that), or any of the myriad of other secondary items that might be needed, nor the labor involved from a dealer or other party. They don't directly mention repairs to the gelcoat, if needed, due to "damage". Presumably they might send a kit, but you'd have to pay someone to empty the pool and do the recoat.
All in all, one of the more worthless warranties I've seen. Time to treat your pool correctly, and just enjoy it. Despite their warranty, the prospects are for many, many trouble free years.

 

[zemurray]

They're not interested in providing a warranty, nor are they concerned with the actual quality of your water.
I'd really recommend just ignoring their warranty and requirements and focus on taking care of your pool with TFP methods.

If you follow their requirements, you'll have frequent algae due to insufficient FC. You're already at or below FC levels today.
FC/CYA Levels

The FC levels are within the TFP recommendation, under the max of 5ppm with the warranty, and right at the iChlor recommendation of 2-4ppm. I don’t think there will be a warranty issue there?

The main issue seems to be the TA level they are recommending. Interestingly my installers left me with a cheat sheet and called for running TA 50-90, so far below what Imagine Pools suggested.

I plan on discussing with the manufacturer and getting something in writing on a TA level that is more aligned with the installer or TFP recommendation. The installer has told me in the past that they have not had any issues with warranty as long as the pool was properly backfilled. I did not ask about gelcoat issues. They will be here tomorrow checking on things so I’ll try and talk to them about it. This pool installer is well known around here and they have a whole team that has been very helpful and responsive through the whole contract.

 

[reggiehammond]

The FC levels are within the TFP recommendation, under the max of 5ppm with the warranty, and right at the iChlor recommendation of 2-4ppm. I don’t think there will be a warranty issue there?

At CYA 50, your min is 2, which you report you're at/around...
FC/CYA Levels

Recommended range is 3-8, and it's wise to target the higher end of the range with a SWCG as why even flirt with dealing with algae when you have this wonderful device that will make FC for you.

My point is that the manufacturer / pool industry point of view re: FC levels is sure to lead you awry.

 

[cwswifty]

Imagine Pools: "Hey, chemistry expert, can we pay you to help us write our warranty stipulations so that no-one would want to or be able to follow them?"

Chemistry Expert: "Say no more. I got you Boo."

 

[zemurray]

Dealer/Installer was out this morning. They told me that in the last 4 years they have had a few structural warranty issues to deal with which were no problem with the manufacturer and got resolved (small cracks around steps on a certain model), and that they have had zero gelcoat warranty issues over a couple hundred pools installed. They have had a couple customers who didn't take care of their pool get some calcium scaling, which they addressed and now maintain those customer pools with no further scaling. They told me not to worry about the high TA values called out in the manual, stated that for years they couldn't even get a manual for Imagine pools, and that they recommend a lower TA, keep the PH in check and not to worry about it. Their main concern with good TA levels is to prevent premature equipment wear or damage, not gelcoat.