pH rise.....and rise again


LifeTime Supporter
Sep 6, 2007
Current test reading, Taylor kit:
FC: 5
TC: 5
TA: 100
pH: 8.2 (was 7.5 Monday) **added 6 cups 31% MA, will retest at noon and add more if needed, which I think it will be.
CYA: 50
CH: ~200....this test kills me. Faint pink/red, 23 drops later MAYBE a hint of blue).

Recently had my 14yr old vinyl liner replaced by original builder. No issues with that at the moment.

Previously w/ old liner I rarely had any issue maintaining recommended pH levels. I used bleach and/or calcium hypo fairly exclusively (pucks ONLY when managed by neighbors when we were on vaca). Added pH down or MA every so often. However, with new pool liner and fill water from well which has a TA of 140, I struggle with pH. I have successfully lowered TA to 100 a few weeks ago. But my pH still rises from 7.4-7.5 up to 7.8+ every 4-5 days. I've gone through about 4 gallons of muriatic acid to maintain control.

I'm currently using cal-hypo exclusively as bleach always tends to raise my pH. I do not know what else to do. Do lower my TA even more? I think so. My testing notes from before new liner install show TA ranging 70-90 consistently w/o pH yo-yo.

I need to keep pH out of upper end range to due suspected iron in fill water/well water. I use sequestrant monthly for maintenance. Had a post about this in April. Prior start up metals thread

I guess my overall question is this:
#1. do new liners tend to push pH higher? Is there something inert in them that causes this? (I've searched, I say no).
#2. is my only recourse to continue to drop TA to my old range of 70-90?

Thanks! This has me vexed.cHappy swimming everyone!

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
Texas, San Antonio/Marion, South-Central Area
Pool Size
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
#1 - no
#2 - probably

Assuming you have no aeration that is driving-up the pH, then you do need to continue with muriatic acod to lower the pH (and TA) to keep it from raising so fast. Bleach is what we call pH neutral because while a large amount can cause a temp-spike in pH, the pH will return to normal. But that's typically for large chlorine increases over 10 (i.e. a SLAM). I would avoid continuous use of cal-hypo as scaling can be a concern for even vinyl. You mentioned that after 23 drops maybe a hint of blue? I have a feeling the CH has already gotten up there.

I use the 10ML water sample for my CH tests so that each drop of R-0012 = 25ppm. You definately want to hit the "baby blue" with your CH test. Do you have a speedstir? It sure makes that test more bearable.


LifeTime Supporter
Sep 6, 2007
Thanks Texas. (TWU grad here; I miss brisket). I have forgotten about the 10ml conversion test protocol! I'll definitely give that a try. And yes, I'm on my last bit of cal-hypo. Then going back to bleach, most likely by Sun/Mon.

And no aeration at all, deep end return pointed downward and shallow end point toward steps with the slightest of ripples.
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