Updated September 2026 — rewritten by Suns Out Buns Out Pools with photos from our own jobs.
A dirty filter is behind more cloudy pools, overworked pumps and “the chemicals stopped working” complaints than anything else we see. This guide covers the three filter types, how to tell when yours needs attention, and what a proper cleaning looks like — using photos from DE filters we’ve torn down on our routes.
How to Tell Your Filter Needs Cleaning
Your filter’s pressure gauge is the best signal. Note the reading right after a cleaning — that’s your clean baseline. When pressure climbs well above it (a common rule of thumb is around 8–10 psi over), flow is dropping and the filter needs service. Other signs:
- Water that stays cloudy even with good chemistry.
- Weak return flow from the jets.
- Algae that keeps coming back after treatment.
- A gauge that barely drops after backwashing (DE and sand) — the filter needs a full clean.
The Three Filter Types
Cleaning a DE Filter: What a Real Teardown Looks Like
Backwashing a DE filter removes some debris, but over time oils and fine particles bake into the grid fabric and backwashing stops working. That’s when the filter has to come apart.
Grids Straight Out of the Tank
A solid coat of debris the pump has been pushing water through.
Same Grids, After the Teardown
Degreased and rinsed back to white before reassembly.
- Shut off the pump and relieve pressure before opening the tank.
- Remove the grid assembly and hose it down thoroughly, working between every grid.
- Soak or treat with a filter cleaner/degreaser when oils have built up.
- Inspect every grid for tears — a torn grid lets DE blow into the pool.
- Reassemble, then add a fresh charge of DE through the skimmer in the amount your filter specifies.
Wear a dust mask when handling dry DE powder, and follow local rules for disposing of used DE.
A Filter That Stopped Filtering
At this point backwashing does nothing.
Rebuilt and Ready
Cleaned, inspected and reinstalled with fresh DE.
Cleaning a Cartridge Filter
- Turn off the pump, release pressure, and remove the cartridges.
- Rinse top to bottom between the pleats — not so hard that you damage the fabric.
- Soak in a cartridge cleaner periodically to break down oils and scale.
- Replace cartridges that are torn, flattened or no longer hold pressure down after cleaning.
Cleaning a Sand Filter
Sand filters are cleaned by backwashing until the sight glass runs clear, then rinsing. Over years, the sand itself wears smooth and clumps, and needs replacing when backwashing no longer brings the pressure down.
How Often?
It depends on bather load, trees and weather — pine and oak pollen season and storm debris both load filters fast around here. Go by the pressure gauge rather than the calendar. On weekly service we watch pressure every visit and schedule a full clean when it’s due.
Why a Clean Filter Matters More Than You’d Think
The filter is where everything the pool catches ends up. When it clogs, three things happen at once: the pump works harder and runs hotter, circulation drops so chemicals don’t reach the whole pool, and fine particles stay suspended as cloudiness. People often respond by adding more chemicals, which costs money and doesn’t fix the flow problem.
Backwashing Correctly (DE and Sand)
- Turn the pump off before moving the multiport or push-pull valve — never switch it while running.
- Backwash until the waste water runs clear, then rinse (on multiport valves) to resettle the media.
- Return to filter and note the new pressure reading.
- On DE filters, recharge with fresh DE after every backwash — backwashing removes it.
Cartridge filters don’t backwash; they’re cleaned by removing and rinsing the cartridges.
Filter Problems and What They Usually Mean
Low pressure is the one people misread: a clean filter doesn’t cause it. Check the skimmer and pump baskets first, then look for air in the pump lid.
Signs It’s Time to Replace, Not Clean
- Grids or cartridges with tears, holes or collapsed pleats.
- A filter that won’t return to its clean baseline pressure after a full cleaning.
- Sand that has clumped or channeled after years of use.
- A cracked tank or leaking band clamp — stop using it and get it inspected.
Common Questions
How often should a pool filter be cleaned?
Go by the pressure gauge rather than the calendar. When pressure rises well above the clean baseline, commonly around 8 to 10 psi over, it’s time. Heavy debris seasons and storms shorten the interval.
Why is there DE powder on the bottom of my pool?
Usually a torn grid or a cracked manifold inside the DE filter is letting powder pass through. The filter needs to be opened and inspected.
Can I just backwash instead of cleaning the filter?
Backwashing helps DE and sand filters between cleanings, but it doesn’t remove oils and fine debris baked into the media. DE grids need a periodic full teardown.
Want it handled? See pool filter cleaning in Spring, The Woodlands, Conroe and Tomball, or Call or text Steven at (832) 447-4236.