pH keeps increasing, can't keep it down

alexdimo

Member
Oct 4, 2019
9
Lake Dallas, TX
Dear fellow pool owners,

I have been facing an issue with the pH levels ever since July. Coincidentally, around that time I switched from granulated chlorine to liquid, but this could be just a coincidence.

Problem definition: pH is constantly above 8.0, most times 8.2 or above. I'm talking about going from 7.5 to above 8.0 in a matter of 3-4 days.

These are the water levels (some measured last night, some measurements are older but consistent through time so I have no reason to believe they've changed):
FC: 3 (I use Liquid Chlorine 10% exclusively)
pH: 8.2
TA: 110 (measured Sept 4th)
TH: 260 (measured Aug 31st)
CYA: 30 (measured Aug 31st)

Things I've done:
-- I have lowered the pH 3 times in the past couple of months using the typical pH-Down products (and Muriatic Acid substitute in one instance), but it keeps climbing.
-- I've backwashed the filter a couple of times, adding D.E. after that.
-- I generally keep the pool clean, vacuuming in a weekly basis (and more often during peak season) and cleaning skimmers every couple of days. Water is clear and algae free.
-- I've added a lot of water due to large evaporation loss. When the weather hit almost 100 here, I would add water almost in a daily basis. September has had much less water addition/replacement though, due to slightly lower temps.

Kits I use:
-- Taylor K1001 for FC and pH (Amazon.com : Taylor K1001 Basic Residential DPD Pool or Spa Test Kit : Swimming Pool Liquid Test Kits : Garden & Outdoor)
-- HTH 6 way kit (Amazon.com : hth Pool Test Kit 6-Way Test Kit (1173) : Garden & Outdoor) for the rest
I understand the second one is not generally among the recommended kits, but we're talking about a very obvious trend here and not just about small deviations in accuracy.

Let me know what you think and what suggestions you might have. I appreciate all the input. :)

Alex.
 

alexdimo

Member
Oct 4, 2019
9
Lake Dallas, TX
One thing I've though of is lowering the TA a bit, since there was a time the TA was around 90 in the past. But, theoretically, I don't see why this would affect anything, since 110 is a perfectly acceptable value. Also, I would hate to deal with Muriatic Acid if not necessary.
 
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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Alex, we generally see pH increasing due to excessive aeration of water and/or an elevated TA that allows the pH to rise faster. It's true that some pools do better with a pH in the upper 7s, but once it climbs over 8.0-8.2 we worry about scale. You mentioned a TA of 110 being perfectly acceptable, and that's a comment we hear often when comparing numbers to general pool industry recommendations. Those are the same ones who say never to let the FC go over 3 ppm with no regard to the CYA relationship. Here at TFP we employ the Recommended Levels - Trouble Free Pool guidance. On that page you'll see your TA has plaenty of room to go down a bit more which should slow the rising of pH while still being good for your plaster. So if you have no forms of aeration right now, I would consider hitting the water with more (wait for it .....) muriatic acid. I know you don't care for it, but it really is the best product. Strong yes, but very efficient and predictable. So I'd knock the pH down to about 7.2 and let it climb back to 8.0 before doing it again. Do that a couple times to bring the TA down to about 80 and see how that works. You can even take the TA down to 70 is it helps.

Keep in mind however we are about to see some water temp changes in the next month or so. When the water temp drops, so too does the "CSI" which is a measurement of how aggressive or hard (potential to scale) your water is. When the water gets really cold, you can allow the TA and/or pH to be slightly elevated and not worry so much about scale. Make sure to use our PoolMath tool to monitor your CSI number. Hope that helps.
 
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YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
11,494
Evans, Georgia
Hey there dude... just wanted to reiterate what Pat said above- you need to use Muriatic Acid instead of dry acid. The reason is that dry acid leaves behind sulphates that can be harmful to plaster and salt water chlorine generators.

We don't want to use any product which increases damage potential and shortens the life of our pools and equipment.

Just stand upwind. Or get the half strength version, which while costs the same and requires you to use twice as much to get the same result, some folks just feel more comfortable using it.

Maddie :flower:
 
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alexdimo

Member
Oct 4, 2019
9
Lake Dallas, TX
So, I got some MA from Home Depot (HDX brand) and added it two nights ago.

Before:
pH 8.2 or above
TA 120

After adding 28 fl oz of muriatic acid:
pH 7.5
TA 110

To be honest, I was expecting TA to drop much more. The Muriatic Acid instructions say that for pH above 8.2 add 16 fl. oz per 10,000 gallons of water. So approximately I needed 28 fl. oz. Still, the TA dropped by only 10 points, even though the pH dropped substantially.

Thoughts?
 
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johnnyleo11

Member
Aug 13, 2019
23
Coastal Virginia
To be honest, I was expecting TA to drop much more. The Muriatic Acid instructions say that for pH above 8.2 add 16 fl. oz per 1000 gallons of water. So approximately I needed 28 fl. oz. Still, the TA dropped by only 10 points, even though the pH dropped substantially.

Thoughts?
I'm using the Pool Math app to calculate the amount of MA I add to my pool. Are you sure of how many gallons your pool holds?
 

alexdimo

Member
Oct 4, 2019
9
Lake Dallas, TX
Correction to above message, 16 oz per 10K gallons. I believe that my pools holds around 17K gallons, and that is kind of confirmed by the drop of pH to 7.5 after adding 28 oz. of MA.
 

JJ_Tex

Bronze Supporter
Jul 17, 2019
388
Prosper, TX (DFW)
As you can see PH is impacted much more by single doses of MA and TA moves more over time. I cant find the actual procedure on here, but basically if you want to lower your MA significantly and somewhat quickly you need to:
1) Lower your PH to low 7's with MA
2) Aerate your pool (turn on all waterfalls, bubblers, etc) to raise your PH
3) Once your PH gets to the high 7's, repeat

This can take several days to achieve, so most people focus on the PH and let the TA fall into place over time.
 

alexdimo

Member
Oct 4, 2019
9
Lake Dallas, TX
Makes sense, and that was my plan too. Let the pH rise and then add MA again. By doing that 2, maybe 3, times I assume I will reach a chemical balance that will retain the pH in comfortable levels for longer.