Introduction
Pool filters are the unsung heroes of every clean, swimmable backyard pool. They trap dirt, debris, and contaminants, keeping water balanced and safe. But like all mechanical systems, pool filters can experience issues — from poor flow to sand in the pool and everything in between.
In this guide, we’ll walk through the most common pool filter problems and match each one with the exact part that will fix it — whether you’re dealing with a cartridge filter, sand filter, or D.E. (diatomaceous earth) filter.
1. Low Water Flow
Symptoms
- Weak return jets
- Slow circulation
- Cloudy water
Possible Causes
- Dirty or clogged filter media
- Blocked pump strainer basket
- Air trapped in the system
Exact Parts That Fix It
- Replacement Cartridge (Cartridge Filters): If you have a cartridge filter, old or clogged cartridges are often the culprit.
- Sand Filter Media (Sand Filters): Over time, sand breaks down and clogs the system.
- D.E. Powder (D.E. Filters): If D.E. is depleted, add fresh powder after backwashing.
- Pump Strainer Basket: Cracks or gaps can let debris through — replacing it improves flow.
- Air Relief Valve: A faulty valve can trap air. A new valve releases trapped air and restores suction.
2. Cloudy or Dirty Water
Symptoms
- Water looks milky or hazy
- Debris isn’t being removed
Possible Causes
- Filter not collecting fine particles
- Improper filter size
- Worn filter elements
Exact Parts That Fix It
- Fine Mesh Cartridge Element: Higher-quality cartridges capture smaller particles.
- Upgraded Sand or D.E. Media: Fresh or special-grade media filters better.
- O-Ring Seals: Worn seals can bypass unfiltered water around the filter.
3. Sand or D.E. in the Pool
Symptoms
- Gritty sand on the pool floor
- Cloudy water after backwashing
Possible Causes
- Broken lateral or standpipe in sand/D.E. filters
- Overfilled D.E.
- Improper backwash
Exact Parts That Fix It
- Filter Laterals (Sand & D.E. Filters): Cracked laterals allow sand/D.E. to enter the pool.
- Standpipe Replacement: A missing or broken standpipe disrupts proper flow.
- D.E. Grids (D.E. Filters): Torn or clogged grids will release D.E. powder.
4. Frequent Backwashing (Sand Filters)
Symptoms
- Filter needs backwashing more often than usual
Possible Causes
- Media is worn out or channeled
- Incorrect media type/grade used
- Multiport valve not sealing correctly
Exact Parts That Fix It
- Replacement Sand: Old sand packed with debris won’t filter properly.
- Multiport Valve (or Valve Spider Gasket): If it’s not sealing/shifting correctly, it can cause short-cycling and more frequent backwashing.
- Pressure Gauge: An inaccurate gauge can make you backwash too early (or too late).
5. High Filter Pressure
Symptoms
- Rapid pressure build-up
- Frequent backwashing required
- Reduced return flow
Possible Causes
- Dirty filter media
- Restriction in plumbing or valves
- Air in the system
Exact Parts That Fix It
- Pressure Relief / Air Bleed Assembly: If it’s stuck or leaking, pressure/air issues can get worse.
- Filter Media Replacement: Sand, cartridges, or D.E. may need replacing.
- Pump Lid O-Ring: A worn O-ring can let air into the system and contribute to erratic pressure.
6. Filter Leaks
Symptoms
- Water leaking around the filter tank, clamp band, or unions
- Drips at the valve or drain plug
Possible Causes
- Worn gasket or O-ring
- Loose fittings or cracked unions
- Drain plug gasket failing
Exact Parts That Fix It
- Tank Seal / O-Ring Kit: Fixes leaks at the clamp band or tank halves.
- Union O-Rings: Stops leaks at plumbing connections without re-plumbing the pad.
- Drain Plug & Gasket: A super common slow leak source on the bottom of the tank.
7. Strange Noises
Symptoms
- Squealing, grinding, rattling, or “gravel” sounds
- Surging flow at returns
Possible Causes
- Air leak on the suction side
- Clogged or damaged impeller
- Worn motor bearings
Exact Parts That Fix It
- Pump Lid O-Ring / Housing Gasket: Often fixes suction-side air leaks that cause noise and surging.
- Impeller (or Impeller Kit): Removes restriction and restores smooth operation.
- Motor Bearings (or Replacement Motor): Grinding that gets worse over time usually points here.
Conclusion
Your pool filter is key to maintaining clean, safe swimming water. When something goes wrong, the right replacement part can save time, money, and frustration. Whether you're tackling low flow, cloudy water, sand/D.E. in the pool, or leaks — knowing what to replace (and why) helps you fix it faster and keep the water clear.
If you’re not sure which part matches your filter model, Benchmark Pool Supply can help you identify the correct replacement so you don’t waste time on returns.
Need help diagnosing your filter issue? Browse our filter parts or reach out to our team for fast help.
