Troubleshooting guide
Pool filter pressure high or low
Your filter gauge is only useful compared with one number: the pressure right after the filter was cleaned. Write that down and the gauge tells you what's going on.
Know your starting pressure
Pentair's cartridge filter guide says to record the "Original Starting Pressure" after cleaning, and to clean the filter when the gauge reads about 10 psi higher, or when you notice a big drop in flow. On a variable-speed pump, the starting pressure depends on the pump speed, so note the RPM with it and compare at the same speed.
Pressure high
- Most often: the filter is dirty and due for cleaning or backwashing (follow your filter's manual).
- A partly closed return valve or blocked return line also raises pressure.
- If pressure jumps right after cleaning, the media may be worn out or clogged with oils or scale.
Pressure low
Low pressure usually means less water is reaching the filter: low water in the skimmer, full skimmer or pump baskets, a closed suction valve, air in the system, or a clogged impeller. Jandy's pump manual says that when there's no air but pressure is still low, debris may be caught in the impeller. See pump not priming.
Pentair also notes its variable-speed pumps measure total head, not outlet pressure, so the pump's pressure reading may not match the filter gauge.
When to get help
If the gauge is stuck, cracked or reads pressure with the pump off, replace the gauge. If pressure climbs fast after every cleaning, or the filter lid, clamp or tank looks damaged, stop and get a tech to look. A damaged filter tank under pressure is dangerous.
Common questions
What should my pool filter pressure be?
There's no single right number. It depends on your pump, plumbing and filter. Record the pressure right after a cleaning and use that as your baseline. Pentair says to clean its cartridge filters at about 10 psi above that starting pressure.
Why is my pool filter pressure low?
Usually something is starving the pump: low water level, full baskets, a closed suction valve, air leaks or a clogged impeller. Check the suction side first.
How do I open my pool filter safely?
Turn the pump off and switch off the breaker, open the air relief valve, stand clear and wait for the gauge to read zero before touching the lid or clamp. Follow your filter's manual exactly when you put it back together.
Related guides
Cloudy pool water
Test first. Cloudy water is usually chlorine, pH or filtration.
Read the guidePump not priming
Pump runs but the basket won't fill. Almost always air or water level.
Read the guideGreen pool water
Green means chlorine ran out. Find out why so it doesn't come back.
Read the guideHeater won't fire
No heat, a flow or pressure code, or an ignition lockout. Flow comes first.
Read the guideSources
- Pentair, Clean & Clear Plus cartridge filter cleaning guide: when to clean, relieving pressure, start-up
- Jandy (Zodiac), FloPro VS-FHP variable-speed pump installation and operation manual: troubleshooting (copy hosted by Hydropool)
- Pentair, IntelliFlo3 VSF / IntelliPro3 VSF installation and maintenance guide: priming, drive LEDs, troubleshooting chart, alarms and warnings
Brand names belong to their owners. Pool Helpline isn't affiliated with or endorsed by any manufacturer. Steps and codes vary by model and year, so always check your own owner's manual.
