pH trends down...normal?

Oly

Gold Supporter
Jun 28, 2017
2,009
Fresno, CA
Pool Size
27000
If you are vigorously shaking the sample to mix the pH reagent then try just gently rolling, flipping the sample once to mix then match color. If you are using a speed stir then carry on and disregard this suggestion.
 

mgtfp

Bronze Supporter
Mar 5, 2020
974
Melbourne, Australia
Pool Size
66000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Astral VX 7T
One thing that could explain pH dropping is scale forming. Your CH looks too low for calcium scale to be a problem. Could there be other minerals in your water? For example Magnesium? Is there any form of deposits building up in your pool?
 

mgtfp

Bronze Supporter
Mar 5, 2020
974
Melbourne, Australia
Pool Size
66000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Astral VX 7T
Looking back at test logs, my FC did go from 7 to 9.5 and then down to 6.5 in that timeframe. Not a huge drop, but did go lower.
That would create only small effects on pH, nothing that would really be noticeable, especially compared to the aeration drift that should occur in the meantime.
 

Rumbleehockey03

Well-known member
Jul 8, 2019
84
Central NC
Pool Size
12500
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Solaxx (Saltron) Reliant / Purechlor R5
One thing that could explain pH dropping is scale forming. Your CH looks too low for calcium scale to be a problem. Could there be other minerals in your water? For example Magnesium? Is there any form of deposits building up in your pool?
Sorry for not responding to this. Never had any scale buildup
 

Rumbleehockey03

Well-known member
Jul 8, 2019
84
Central NC
Pool Size
12500
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Solaxx (Saltron) Reliant / Purechlor R5
Ph dripped to 7.2 from 7.5 on 16may test and is the same now. No cya has been added since mid-April but have had approx 1.5” of rain over the course of a few weeks. Ph remained at 7.2 as of yesterday.
 

magiteck

Gold Supporter
May 20, 2020
518
Neenah, Wisconsin
Pool Size
13600
Surface
Vinyl
Chlorine
Liquid Chlorine
Do you cover your pool? When mine is covered, the pH trends down in the low 7s, especially after rains. When I leave it open, it trends upward, to the high 7s.
 

Rumbleehockey03

Well-known member
Jul 8, 2019
84
Central NC
Pool Size
12500
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Solaxx (Saltron) Reliant / Purechlor R5
Do you cover your pool? When mine is covered, the pH trends down in the low 7s, especially after rains. When I leave it open, it trends upward, to the high 7s.
Not typically. I did have it covered last week with a solar cover when we had a late winter spell 🤣 as noted though, I’ve NEVER had my ph increase naturally without aerating.
 

Rumbleehockey03

Well-known member
Jul 8, 2019
84
Central NC
Pool Size
12500
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Solaxx (Saltron) Reliant / Purechlor R5
So another week on…sunny week, no rain, added a little fill yesterday evening, steady 7.2. Turned on my fountain and aimed it straight down to start aeration because my TA is at 100 now, I guess from adding borax overtime…don’t want TA any higher based on pool school. Also likely to need CYA soon as water warms up and degradation will kick in soon. Water temp is 87 now…right where we like it 🙂 no problems, just reporting
 

CeltiaK

Active member
May 8, 2014
27
Western Mass.
I’m another one who has down-trending pH. We’ve had a pool for many years, and every summer is the same.
- We do a partial drain for winter, and fill with tap water in spring. I think TA of the tap water is atound 50.
- TA starts the season around 50ish, but as I bring up FC and Salt, it rises to about 60 and stays there. I don’t mess with it.
- When I add CYA, pH does drop. If pH is low to start (7.2), I aerate by aiming my jets high.
- Pool is almost always covered with a solar blanket except when swimming or cleaning.
- We live in the NE and I always assumed acid rain was the driver.
- I add Borax whenever I get to 7.2 - I take it to 7.5-7.6. This is maybe 3-4 times from June to September. I love adding Borax - makes the water and our suits smell great. I would really love to borate my pool, but with the annual drain, it seems like a waste.
- I have never added acid to my pool. I have an unopened gallon of muriatic freaking me out in my garage. How to dispose of it if I never need to consume it?
- I once tried raising pH to 7.8, but it made the water feel slimy (to me) and it lost a bit of sparkle. I prefer the low end of the pH range. But that’s my pool, my region.
- I would like to get a heater, but my CH is much too low for that (75). When I do buy a heater and raise my CH, maybe something will shift in my pH balance.

If it ain’t broke don’t fix it. Enjoy your pool and appreciate that you may never have to deal with acid.
 

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