PH variation from 7.2 to 7.8 in a week regularly - normal?

[norcalpool1]

Replastering was done on this pool 2.5 months ago. Every week I have been noticing that the pool service adds acid to bring the PH level to 7.2. PH level then starts increasing and at the end of the week, it is at 7.8. Is that normal or should the PH be expected to stay within a smaller range?

Current results (middle of a pool service week) from TF-100:
PH: 7.5
TA: 50 ppm
CH: 500 ppm
CYA: 60
FC: 7
CC: 0
Water temperature varies from 78 to 82 (solar heating).
Phosphates (Leslie's measured it) - high and out of range, but don't remember the number

Every week, I add about 50 cf of fresh water (375 gallons) an hour or so before the pool service adds acid to compensate for evaporation (3/16" - 1/4" per day. That is about 2.75% of the pool's total volume. Before adding fresh water the PH is around 7.7 or 7.8 already. Pool service then adds enough acid, and I measure the PH the next morning, and it is usually at 7.2.

Fresh water chemical levels is at
TA: 90
PH: 8.4+
CH: 30

 

[ajw22]

I would not lower your PH below 7.6. Keep your PH between 7.6 and 8. Add MA when PH is 8 to lower it to 7.6-7.8.

That PH rise is normal for new plaster. It can take a year for plaster to fully cure and stop raising PH. Your fill water PH is not helping.

 

[mknauss]

If you follow Allen's recommendation, you need to add the acid as it will be needed more often.

If you have a TF100, why do you have a pool service? You can manage this -------

I assume you use Trichlor to chlorinate. It would be best to switch to liquid chlorine now so your CYA does not rise further.

Take care.

 

[norcalpool1]

The trichlor tablets are not used. Liquid chlorine is in use. I feel I could maintain the pool myself with the recent practice with the testkits and following the posts, but I am frequently out of town for long periods at a time and so I find it useful to have the weekly pool service. But I do monitor the chemicals myself periodically.

 

[mknauss]

I find it difficult to believe a pool service can just add liquid chlorine once per week and the FC be above minimum the entire week.

Get a SWCG. Eliminates the need to add chlorine every day. pH is what you must monitor the most.

We leave for weeks at a time without issue.