Every pool filter gets a score from 0 to 100% built from five factors, which maps onto the 5-point rating shown on the site (a 0% score would be 1.5 stars; a perfect score, 5). Each factor is scored against fixed reference points, not against the other products in the list, so adding a new model never moves another model’s rating. Filters are grouped by type (sand, cartridge and D.E.), and value and filter area have their own scale for each type.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per gpm of rated flow | 35% |
| Filter area | how much filter there is, which sets how long between cleanings | 30% |
| Valve | how easy it is to backwash | 10% |
| Pressure rating | maximum working pressure of the tank | 10% |
| Warranty | warranty on the tank | 15% |
Where the numbers come from
Flow, filter area, tank size, pressure rating and warranty come from the maker’s spec sheet, manual or product page. When a sand filter’s maker gives only the tank diameter, its bed area is worked out from that and marked as estimated. Prices are checked at Amazon, the maker’s own store and pool supply retailers, and the lowest is used.
The factors
Value is the current price divided by the rated flow in gallons a minute, on a log scale, so going from $16 to $8 per gpm counts as much as going from $8 to $4. For sand filters, $20 per gpm scores zero and $6 full marks; for cartridge, $20 and $5; for D.E., $30 and $9.
Filter area is how much filter there is, which sets how long it runs between cleanings. Sand scores zero at 1.5 sq ft of bed and full marks at 5; cartridge, 100 and 500 sq ft; D.E., 20 and 72 sq ft.
Valve is how easy the filter is to backwash. A multiport valve scores full marks; a push-pull or slide valve scores 60. Cartridge filters, and D.E. filters cleaned without backwashing, need no valve and score full marks here. A filter sold without its valve gets the neutral middle score.
Pressure rating is the tank’s maximum working pressure: 30 psi scores zero and 50 psi full marks.
Warranty is the warranty on the tank: no warranty scores zero and 3 years full marks. Filters bought online often get a shorter warranty than from a pool dealer, and the online cover is what’s scored.
What isn’t scored
Pool size rating, port size, sand weight and air relief are listed but not scored. Filters for above-ground pools have their own page.
Missing data
If a figure isn’t published, that factor gets the neutral middle score (50) and the product page marks it as estimated.
Ties and discontinued models
Products are ranked by score within each group. Discontinued models stay listed but rank below every current model and can be hidden with the “Hide discontinued” filter.