pH rising too quickly

tredos1

Member
Mar 11, 2017
24
Round Rock, Texas
Hi all,

I've always felt that my pH wanted to rise too quickly but I never asked about it. I've been using the bleach/HCl method for a few years and recently switched to SWG. Since the SWG might have a tighter tolerance for pH I thought I would seek guidance. I lowered my pH with acid just recently. pH in 8/5 was between 7.4/7.6, on 8/6 was 7.6 and this morning was 7.8. That seems to fast to me. The VSP running at 2250 RPM for 12 hours/day and the SWG was running at 60%, but I just lowered it to 50% since the chlorine was still climbing over when I was using bleach. Anyone have some insight? it's been this way for years. The pool really likes to be around pH 8 or 8.2. New plaster is about 16 months old, but I had the same problem with the old plaster too.
Here's the full set of water parameters. I know CH is low, but the CSI is fine so I haven't upped it and I know CYA is low for SWG, but the generator is keeping up, likely due to some shade on the pool.
Temp: 86, Chlorine: 7.2, CYA: 30, pH: 7.8, TA: 80, CH: 260, Salt: 3600
 

JJ_Tex

Bronze Supporter
Jul 17, 2019
1,637
Prosper, TX (DFW)
My numbers look very similar to yours (except CYA, get that one up). There is no need to try and keep your pH in the low 7's. Just wait for it to hit 8, and knock it down to the mid 7's. That will keep your CSI happy and you wont spend all of your time fighting pH.
 

tucsontico

LifeTime Supporter
Mar 30, 2014
275
Tucson, AZ
When I installed my SWG about 6 years ago, I had a similar problem. The pH was climbing almost daily due to the carbonation effect in the SWG. I solved the problem by installing a Pentair IntellipH acid injecting system. My pH is now extremely stable (7.4-7.6) because a small amount of MA is being added each day. Lots of DIY info on the forum of how to do this with different brands of equipment. Good Luck!
 

Rattus Suffocatus

Silver Supporter
Jun 5, 2019
1,192
Corona de Tucson, AZ
SWCGs in addition to making H2 gas O2 gas Cl- ions also generate a good amount of OH- ions which does generate some NaOH on top of everything else. So just running a salt cell does create the chemicals for the rise in pH. Wikipedia even claims that the chlorine generated is ultimately sourced from muriatic acid additions. I add a full cup, 8 floz, once or twice if I feel like it every week which is much worse than when I did liquid chlorine. As cool as an automatic doser sounds, once a week is still very easy to do and adequate enough to keep CSI balanced enough to keep scaling from happening. Hauling a couple of bottles of HCl every three months or so is still much more desirable than the bleach.
 

Rattus Suffocatus

Silver Supporter
Jun 5, 2019
1,192
Corona de Tucson, AZ
What's your TA? If it's high then eventually it will start coming down (unless you are using a lot of high TA fill water--if so consider a solar cover when not in use if you already aren't using one) and then the rate of pH rise will slow down a bit.

HCL will break down to water and or H2 gas and CL- in the water so it's pretty pure and safe to add as long as your CSI is in a good range, it should be fine to do,. You can let your CSI swing more as long as the average in a week is just slightly negative for the SWCG, you should be fine, So you don't have to add it as often as you are.. the amount over time, yes... the frequency of every of couple of days? No.
 

Rattus Suffocatus

Silver Supporter
Jun 5, 2019
1,192
Corona de Tucson, AZ
No.. that's actually on the low end. Mines at about 100. Again.. it's a part of having a SWCG. If you drop to TA of 60 or lower then you might need to consider borates (look in the articles) or other means of buffering pH in the future. But I do think you are okay for now. Even if you had to add something to raise TA and lower pH, as long as it's a "once a year" thing, then I wouldn't be to concerned.
 

JJ_Tex

Bronze Supporter
Jul 17, 2019
1,637
Prosper, TX (DFW)
TA of 80 is just fine. I think the point I'm trying to make is that it is absolutely okay to leave your pH of 7.8 alone, and frankly that is close to where it wants to be.

It doesnt want to be a 7.2 or 7.4, so it will quickly jump up to 7.6, then a bit slower to get to 7.8 and even slower to 8.0. Let it hang out at 7.8 and dont try to add acid until it gets in the 8's and save yourself some frustration of trying to keep your pH below where it wants to be.
 

Rattus Suffocatus

Silver Supporter
Jun 5, 2019
1,192
Corona de Tucson, AZ
With the lower TA, a higher pH is better for a neutral CSI. Good point there and correct. Use Pool Math, don't worry so much about the individual numbers (even when Pool Math complains about them unless one is waaay out of range for some reason) and shoot for a slightly negative CSI (you want the water slightly acidic for the salt cell's health). Don't worry about adjusting the CSI more than once a week. You will be fine at once a week.