Pool Filter Is Leaking
Filter leaks are usually sealing-surface problems, and the location tells you which. They waste water, drop pressure and, on a tank under pressure, deserve prompt attention.
Likely Causes
Tank o-ring or band clamp
The seam between tank halves leaks when the o-ring is dry, pinched, dirty or flattened, or when the clamp is not seated evenly.
Air relief valve
The relief assembly and its o-ring are small, exposed and frequently the source of a fine spray.
Multiport valve spider gasket
On sand filters, a worn spider gasket sends water continuously to waste — a leak you may only notice on the water bill.
Cracked tank
Sun degradation and age produce hairline cracks. This means tank replacement.
Plumbing connections
Unions and threaded fittings at the filter inlet and outlet.
Pressure gauge port
A worn or improperly sealed gauge fitting can weep.
What You Can Safely Check
- Dry the tank, run the system and watch where water first reappears
- Note whether the leak happens only under pressure
- On sand filters, check whether water runs continuously from the waste line
When to Call a Professional
Cracked tanks and multiport valve failures need replacement parts. O-rings and relief valves are quick repairs — worth doing before they become the reason you lose a day's water.
Safety: Always relieve pressure with the air relief valve before loosening a filter band or clamp. Pressurized tanks have caused serious injuries.