Pool Filter Sand & DE Calculator
Find out how much sand or DE powder your pool filter needs. Enter your tank diameter or filter area for exact pounds, bag counts, and backwash recharge amounts.
Safety
Adding too much sand raises tank pressure and can crack the laterals or the valve when you reassemble; too little lets water channel past unfiltered. When loading sand, half-fill the tank with water first to cushion the laterals and keep the standpipe centered and covered. For DE, add the slurry slowly through the skimmer so it coats the grids evenly rather than slugging through.
Media quantity follows the filter, not the pool. A sand filter takes about 100 lbs at a 16″ tank and roughly 25 lbs more per inch of diameter — a 24″ tank holds around 300 lbs of #20 silica, six 50-lb bags. A DE filter takes 1 lb of DE per 10 sq ft of grid area, or about 80% of that after a backwash. The plate on the tank always overrides the chart.
How Much Sand or DE Does a Pool Filter Need?
The amount of media is set by the filter itself, not the pool. For a sand filter it follows the tank diameter; for a DE filter it follows the grid area in square feet. Pool volume and pump size don't enter into it — a bigger pool needs a bigger filter, but once you own the filter, the media it holds is fixed. The one number that always wins is the sticker on the tank, which lists the exact charge for your model.
Sand quantity by tank diameter
Sand filters start around 16" and take roughly 100 lbs, climbing about 25 lbs per inch of diameter. Sand is sold in 50-lb bags of #20 silica (0.45-0.55 mm), so the table also gives the bag count to buy.
| Tank diameter | #20 silica sand | 50-lb bags |
|---|---|---|
| 16" | 100 lbs | 2 |
| 18" | 150 lbs | 3 |
| 20" | 200 lbs | 4 |
| 22" | 250 lbs | 5 |
| 24" | 300 lbs | 6 |
| 27" | 350 lbs | 7 |
| 30" | 525 lbs | 11 |
| 36" | 875 lbs | 18 |
Estimate from tank diameter, rounded to the nearest 25 lbs. Deep tanks (e.g. Pentair Triton II) can need more — the plate on the tank always overrides the chart. Never substitute play or construction sand.
DE quantity by filter area
A DE filter is charged at 1 lb of DE per 10 sq ft of grid area for a new or fully cleaned filter. A routine backwash strips most of the cake but leaves about 20% on the grids, so you only recharge with ~80% of the full amount. A standard DE scoop holds about 0.5 lb, which is the easiest way to measure at the pad.
| Filter area | Full charge | After backwash | Scoops (full) |
|---|---|---|---|
| 24 sq ft | 2.4 lbs | 1.9 lbs | 5 |
| 36 sq ft | 3.6 lbs | 2.9 lbs | 7 |
| 48 sq ft | 4.8 lbs | 3.8 lbs | 10 |
| 60 sq ft | 6.0 lbs | 4.8 lbs | 12 |
| 72 sq ft | 7.2 lbs | 5.8 lbs | 14 |
Full charge for a new or fully cleaned filter at 1 lb / 10 sq ft. Hayward publishes ~1.25 lb / 10 sq ft, so round up on their filters and confirm against your manual.
Getting the amount right matters
Too much sand raises tank pressure and can crack the laterals or the valve when you close the filter back up; too little lets water carve channels straight through, so it looks like the filter is running while nothing gets caught. Load sand into a tank that is half-filled with water first — it cushions the laterals — and keep the standpipe centered and capped so grains don't fall into it. For DE, mix the powder into a slurry and pour it slowly into the skimmer nearest the pump so it coats every grid evenly; dumping it in a slug leaves bare patches that pass debris.
Not sure of your filter size?
If you're still choosing equipment rather than refilling it, start with the pool filter size calculator to get the square footage your flow rate needs, then size the pump against it. Both work best from a real pool volume figure rather than the number on the build contract.