Fluctuating PSI reading

[Zinnia]

Current test reading: FC 5
CC 0
PH 7.8
TA 80
CH 220
CYA 35

Pool was brushed, vacuumed and backwashed three days ago.
Early in the AM the PSI will be normal (14 to14.5) but by midday pressure rises to 18 then will drop by again in late evening. Any thoughts on why? We have been having extreme heat (fourth day of 93+) and are in a drought. Temps are predicted to drop in the next day or so. Ready to close the pool but waiting for water temp to drop. Just trying to maintain water level and am not able to add additional water from well (already drained it once). Not wanting the pay for hauled in water this late in the season. A long backwash is not possible. Any help would be greatly appreciated.

 

[Bama Rambler]

Do you have a glycerin filled gauge? I so, try equalizing it to atmosphere during the hot part of the day.
If you don't have a filled gauge, then the heat may be expanding something in the plumbing or equipment causing a flow restriction. However, that's extremely unlikely.

 

[Swampwoman]

Okay, so if you don't want to add well water to the pool after trucking in water, I understand but I'm not sure how lse you can keep your filter clean

Maybe if you do a Deep Clean of the filter, that will restore normal pressure? Just search for that title in the forum.

 

[mas985]

Early in the AM the PSI will be normal (14 to14.5) but by midday pressure rises to 18 then will drop by again in late evening.

Do you have solar? When it turns on, pressure will rise and when it reaches temperature, it will then turn off.