Question 1

What size pool filter do I need for a 15,000 gallon pool?

Accepted Answer

For a 15,000 gallon pool with an 8-hour turnover, you need 31.3 GPM. That points to a 100-120 sq ft cartridge filter, a 19-22 inch sand filter, or a 48 sq ft D.E. filter. Always pick a filter rated for slightly more flow than required so it doesn't run at its max capacity constantly.

Question 2

What size pool filter do I need for a 24,000 gallon pool?

Accepted Answer

A 24,000 gallon pool at 8-hour turnover needs 50 GPM. That means a 150 sq ft cartridge (like a Hayward C150S), a 24-26 inch sand tank (Hayward S244T or S270T), or a 48-60 sq ft D.E. filter. Step up to a 22-inch sand filter or 150+ sq ft cartridge if you have a lot of trees, pets, or heavy bather load.

Question 3

What size pool filter do I need for a 30,000 gallon pool?

Accepted Answer

A 30,000 gallon pool at 8-hour turnover needs 62.5 GPM. The sweet spot is a 200 sq ft cartridge (Hayward SwimClear C200S, Pentair Clean and Clear 200), a 27-30 inch sand filter (Hayward S270T or S310T), or a 60 sq ft D.E. Grid filter. At this size, a variable-speed pump saves hundreds per year vs single-speed.

Question 4

How do I read the Hayward pool sand filter size chart?

Accepted Answer

Hayward sand filters use S-series model numbers where the digits indicate tank diameter in inches. S166T is a 16-inch tank (~35 GPM max), S244T is 24 inches (65 GPM), S310T is 31 inches (112 GPM). Pick a model whose max flow exceeds your required GPM but doesn't blow past your pump's actual output. Pentair's Tagelus and Sand Dollar series use similar logic.

Question 5

Is it OK to oversize a pool filter?

Accepted Answer

Yes, and it's usually a good idea. An oversized pool filter traps more dirt between cleanings, runs at lower head pressure (which saves pump energy), and filters finer particles because water moves through it more slowly. The downside is upfront cost: a 420 sq ft cartridge filter for a 15,000 gal pool costs 2x a 100 sq ft filter but lasts longer between cleanings.

Question 6

Cartridge, sand, or D.E. filter: which is best?

Accepted Answer

D.E. filters clean finest (down to 2-5 microns), cartridges are mid-range (10-15 microns), sand is coarsest (20-40 microns with a clarifier). Cartridges are easiest to maintain (hose off, no backwash). Sand is cheapest to run but needs weekly backwashing. D.E. is best water quality but needs monthly backwash and fresh D.E. powder each time.

Tank Diameter	Sand Needed	Max Flow (GPM)	Good For
16 in	100 lbs	30 GPM	Up to 14,000 gal
19 in	150 lbs	40 GPM	Up to 19,000 gal
22 in	200 lbs	50 GPM	Up to 24,000 gal
24 in	250 lbs	60 GPM	Up to 29,000 gal
26 in	300 lbs	70 GPM	Up to 34,000 gal
30 in	450 lbs	90 GPM	Up to 43,000 gal
36 in	650 lbs	130 GPM	Up to 62,000 gal

Pool Filter Size Calculator

Pool Filter Sizing Rules

Required Flow Rate

Pool Sand Filter Size Chart

Hayward Pool Sand Filter Size Chart

Hayward and Pentair Cartridge Filter Sizing

Frequently Asked Questions