Pool Filter Cleaning Procedure Reference

Why this matters

A pool filter accumulates debris and biological matter from the water; when restricted, flow drops, the pump strains, water clarity declines, and chemistry stresses build. Cleaning is straightforward once you know the type, and the wrong procedure damages the filter (DE filter "regenerated" wrong, cartridge cleaned with high-pressure water that splits the pleats). Know the type, follow the manufacturer's PSI / vacuum threshold, and the filter delivers years of service.

Three filter types

Sand filter:

• Cylindrical tank filled with #20 silica sand (or zeolite)
• Water enters top, flows down through sand bed, exits bottom through laterals (small slotted pipes)
• Traps debris in the sand bed
• Cleaning: BACKWASH (reverse flow flushes debris out to waste line)
• Lifespan: sand is replaced every 5-7 years (loses sharpness, can't trap fine debris)

DE (Diatomaceous Earth) filter:

• Tank contains a grid of fabric-covered "fingers" that DE powder coats
• DE is very fine; traps very small debris (down to 1-3 microns)
• Cleaning: BACKWASH then RECHARGE with fresh DE through the skimmer (or "bump" the manual handle to redistribute)
• Periodic full-strip (3-12 months): disassemble, hose grids clean, reassemble, recharge
• Lifespan: grids last 5-10 years; DE replaced every cleaning

Cartridge filter:

• Tank with replaceable pleated cartridges
• Water flows from outside-in across the pleats
• Cleaning: REMOVE and HOSE off the cartridges (no backwash valve)
• Lifespan: cartridges 1-3 years depending on use and water chemistry

Cartridge filters are most common in new residential installations; DE filters in older premium installs; sand filters universal but less effective at fine filtration.

When to clean - PSI threshold

Every pool filter has a starting pressure (read after a fresh cleaning) - typically 10-15 psi at the inlet pressure gauge. As the filter loads with debris, pressure climbs. Manufacturer's rule: clean when pressure is 8-10 psi ABOVE the starting pressure.

Example: starting pressure 12 psi → clean at 20-22 psi.

Some signs in addition to pressure:

• Visible reduction in flow at the return jets
• Reduced reach of cleaning suction
• Cloudy water that doesn't clear with chlorine adjustment
• Pump motor running hotter than normal (high head pressure)

Sand filter - backwash procedure

Time: 10-15 minutes.

Tools: None specific (pool tools are usually onsite).

1. Power off the pump.
2. Position the multiport valve to BACKWASH. Don't move the handle with the pump running - it damages the diverter gasket.
3. Open the waste / sewer line if the system has a separate valve.
4. Start the pump. Watch the sight glass on the side of the multiport.
5. Run backwash 2-3 minutes, until the sight glass shows clear water (no longer cloudy/brown).
6. Power off the pump.
7. Position multiport valve to RINSE.
8. Start pump, run 30-60 seconds to settle the sand bed.
9. Power off, position multiport to FILTER (normal operation).
10. Restart pump. Pressure should now read the starting / clean pressure.

If pressure stays high after a thorough backwash, the sand may be channeled (water finds a path of least resistance) or the sand is at end of life. Recommend sand replacement.

DE filter - backwash + recharge procedure

Time: 15-25 minutes.

Tools: DE powder (sized per the manufacturer; typical residential filter takes 1-3 lb), measuring cup, pool brush for skimmer recharge.

1. Power off pump.
2. Multiport valve to BACKWASH.
3. Start pump, run 2-3 minutes until water clears.
4. Power off pump, switch to RINSE, run 30-60 sec.
5. Power off, switch to FILTER.
6. Recharge with DE through the skimmer:

• Measure DE per manufacturer (typically 1 lb per 5 sq ft of filter area)
• Mix DE with water in a 5-gallon bucket to form a slurry
• With pump running, pour slurry into the skimmer slowly
• DE coats the filter grids as water passes through

1. Pressure should now read starting pressure.

Full-strip cleaning (every 6-12 months):

1. Power off, drain the filter tank
2. Open the tank (usually a clamp band)
3. Remove the grid manifold assembly
4. Hose each grid thoroughly outside the tank
5. Inspect grids for tears, blown-out areas; replace if damaged
6. Reassemble with all gaskets seated; clamp band tight
7. Refill, recharge with DE as above

Cartridge filter - clean procedure

Time: 20-40 minutes.

Tools: Garden hose with nozzle, sometimes a cartridge cleaning solution (TSP or commercial cartridge cleaner) for periodic deep clean.

1. Power off pump.
2. Open the air bleed valve on top of the filter (release pressure).
3. Open the drain plug at the bottom; let tank drain.
4. Remove the clamp / lockring holding the tank halves.
5. Lift off the top half of the tank.
6. Remove the cartridges (1-4 cartridges typical for residential).
7. Hose each cartridge thoroughly from top to bottom, BETWEEN the pleats. Don't use high pressure (no pressure washer - splits pleats). Standard garden-hose pressure is right.
8. Inspect for tears, missing pleats, end-cap damage. Replace if damaged.
9. Reassemble: install cartridges in correct orientation (some have ribbon-side or marked end), seat lid gasket, tighten clamp.
10. Open the air bleed.
11. Start pump; close the air bleed when water sprays out.
12. Verify pressure returns to starting pressure.

Deep clean (every 3-6 months in heavy use): soak cartridges in a cleaning solution overnight after initial hose-off. Removes embedded oils, sunscreen residue, biofilm.

Common cleaning mistakes

• Backwashing a cartridge filter (there's no multiport valve to backwash) - wastes pump cycle
• Pressure-washing cartridges - splits pleats; cartridges leak fine debris into pool
• Skipping the RINSE step on sand/DE - backwash debris settles back into the filter; pressure stays high
• Wrong DE amount - too little = unfiltered water; too much = clogs filter
• Running pump without DE after a backwash → debris passes straight through the empty grids into the pool
• Not opening the air bleed before pressurizing → trapped air blocks flow; pressure gauge reads erratic
• Forgetting to switch multiport back to FILTER → water cycles to waste line, drains the pool slowly

Replacement intervals

• Sand: every 5-7 years
• DE grids: every 5-10 years (or when torn)
• Cartridges: every 1-3 years (or when pressure won't return to starting after thorough cleaning)
• Cartridge filter housing O-rings: every 1-2 years

Pressure gauge accuracy

References

• Manufacturer manuals (Hayward, Pentair, Jandy, Sta-Rite) - for filter-specific cleaning procedures and DE amounts
• APSP (Association of Pool & Spa Professionals) maintenance guidelines
• ANSI/APSP-15 (American National Standard for Residential Swimming Pools)
• IPSSA Service Technical Reference Manual