Filter PSI
Last reviewed August 12, 2026
What to do at each reading
| Reading vs clean baseline | What it means | What to do |
|---|---|---|
| At baseline | Filter is clean | Nothing |
| Up to +5 | Normal loading | Nothing |
| +5 to +8 | Filling up | Note it — likely due next visit or the one after |
| +8 to +10 | Service trigger | Cartridge: pull and clean. DE: backwash and recharge. Sand: backwash and rinse. |
| At or below baseline, weak flow | Suction-side problem | Check pump basket, skimmer basket, then suction-side air leak |
| High and flat between backwashes | Channeling or restriction | Sand: suspect mud-balling or media at end of life |
Sand triggers slightly earlier than the others, around +7 to +10.
The baseline is the whole rule
PSI on its own means nothing. 22 PSI is fine on one pool and a service call on another. What matters is the gap from that filter's own clean baseline.
The baseline is the reading straight after a fresh clean, a DE recharge, or a backwash and rinse. Record it on the customer card the first time you establish it, because the next tech has no way to derive it.
No recorded baseline? Use 10–15 PSI as the residential stand-in until you can set a real one, and set one at the next clean.
When the number lies
- Brand new install — no baseline exists yet. The first two or three visits establish it.
- Bad gauge — a stuck gauge reads low and hides a loading filter. Tap it gently; if the needle doesn't move at all, suspect the gauge before the filter.
- Variable-speed pump — PSI is lower at lower RPM. Compare readings taken at the same speed or you are comparing nothing.
- Air in the system — pressure spikes and wanders. Bleed the air before trusting the reading.
Why it is worth logging every visit
One reading tells you whether to service the filter today. The series tells you the filter's health. A pool that used to take eight weeks to climb 8 PSI and now takes three is telling you the media or the element is near the end, well before anyone complains about the water.
Logging chemistry on every stop? PoolSpartan keeps the readings, works out the LSI as you type them, and sends the customer a service report when you close the visit. Free to start. We only get paid when you do.
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