The filter is the kidney of a pool — pick the wrong type and you're fighting clarity problems all season. Every pool tech has a preference, and every homeowner has a budget. This guide cuts through the marketing and compares the three filter technologies on what actually matters in the field: filtration quality, maintenance burden, water waste, and total cost of ownership.
Sand filters push water through a bed of #20 silica sand (or zeolite, or glass media). As debris accumulates in the sand bed it actually improves filtration — until pressure climbs too high, at which point you backwash by reversing flow. Sand filters trap particles down to about 20–40 microns. They're the oldest technology, the most forgiving, and the easiest to service.
DE filters use a powder made from crushed fossilized diatoms — microscopic algae skeletons — coated on fabric filter grids. The coating captures particles as small as 2–5 microns, making DE the gold standard for water clarity. When pressure rises you backwash, then recharge with fresh DE powder. The grids require annual disassembly and cleaning.
Cartridge filters push water through pleated polyester fabric elements. They require no backwashing — when the element gets dirty you simply remove and hose it off. Filtration sits in the middle at 10–15 microns. They use zero water for cleaning, making them popular in drought-prone states like California and Nevada.
| Factor | Sand | DE | Cartridge |
|---|---|---|---|
| Filtration (microns) | 20–40 | 2–5 | 10–15 |
| Water clarity | Good | Excellent | Very good |
| Backwash required | Yes | Yes | No |
| Water wasted per service | 50–100 gal | 100–200 gal | 0 gal |
| Annual maintenance | Backwash + yearly sand change every 5 yr | Backwash + annual grid cleaning | Cartridge rinse + replacement |
| Upfront cost | $ | $$$ | $$ |
| Media replacement cost | $30–50 (sand) | $25–60 (DE powder) | $50–150 (cartridge) |
| DIY-friendly | Very easy | Moderate | Easy |
Sand filters dominate commercial and rental installations because there's almost nothing to break. A multi-port valve with 6 positions covers every operation: filter, backwash, rinse, recirculate, waste, and closed. Common residential models include the Hayward Pro Series and Pentair Sand Dollar.
Pro tip: Replace standard silica sand with ZeoSand or FilterGlass to cut filtration to 5–10 microns without changing the tank — a $40–70 upgrade that makes a noticeable clarity difference.
If a customer complains about perpetually dull water despite good chemistry, the answer is almost always a DE filter. The 2–5 micron threshold catches dead algae cells, fine dust, and sunscreen residue that sand and cartridge miss entirely. Hayward Pro-Grid, Pentair FNS Plus, and Jandy DEV are the dominant residential lines.
Never backwash DE into a septic system or storm drain in jurisdictions that prohibit it. DE powder can clog drain fields. Check local regulations before every installation.
Cartridge filters win on water conservation and simplicity for above-ground and smaller residential pools. They also run at lower system pressure, which reduces strain on pump seals. Hayward Star-Clear, Pentair Clean and Clear, and Sta-Rite System 3 are the most serviced units in the field.
The right filter depends on the pool's specific context:
Track filter pressure readings over time with PoolLens. Log the clean starting pressure for each pool so you and every tech on your team know the exact backwash trigger point.
Before recommending a filter swap, consider media upgrades. Zeolite in a sand tank improves filtration to 5 microns and also adsorbs ammonia — a bonus for pools with heavy bather load. For DE filters, consider switching to a D.E. Alternative (perlite-based) in areas with disposal restrictions.
| Cost Factor | Sand | DE | Cartridge |
|---|---|---|---|
| Initial filter unit | $300–600 | $500–1,000 | $350–750 |
| Media/consumables (5 yr) | $50 | $200 | $300 |
| Water waste (5 yr) | $25–75 | $50–150 | $0 |
| Labor (annual clean) | Low | High | Medium |
PoolLens stores baseline pressure data per pool so any tech on your team backwashes at the right time — not too early, not too late.
Open PoolLens Free →DE (diatomaceous earth) filters provide the finest filtration at 2–5 microns, followed by cartridge filters at 10–15 microns, and sand filters at 20–40 microns. For the clearest water, DE wins.
Backwash a sand filter when pressure rises 8–10 PSI above the clean starting pressure, typically every 2–4 weeks during swim season.
Generally no — the tank, valve, and plumbing are sized specifically for each filter type. It's more cost-effective to replace the entire filter unit.
Cartridge filters are the best choice for water conservation because they require no backwashing. Sand and DE filters waste 50–200 gallons per backwash cycle.