Pick your filter's tank size — get the sand weight, bags to buy, and the glass-media alternative.
Why the sand spec matters
Filter sand isn't sand-sand: #20 silica's grain size (about half a millimeter) is what traps debris while letting water pass. Finer play sand packs and channels; coarser sand lets everything through and can shred through the laterals into your pool. The $12 bag with "pool filter" on it is the only right answer.
Sand vs glass media, honestly
Glass filters slightly finer, resists channeling, and lasts longer (10+ years claimed) at roughly triple the price per change but 20% less weight needed. On a 5–7 year sand cycle costing ~$50, the economics are nearly a wash — glass wins on filtration finesse and fewer backwashes, sand wins on being available everywhere for cheap. Neither choice is wrong.
The change-day checklist
Old sand out (shop vac beats hands), inspect every lateral for cracks while it's empty (this is the only cheap time to replace one), tank ⅓ full of water, pour slow, top up, backwash before first filter run. Then note your clean pressure on the cheat sheet — new media resets the baseline your backwash timing depends on.
Frequently asked questions
How much sand does my pool filter need?
By tank diameter, the standard amounts run: 16" ≈ 100 lbs, 19" ≈ 150, 21" ≈ 200, 22" ≈ 250, 24" ≈ 300, 30" ≈ 500. Your filter's label or manual states the exact capacity — this page gets you to the store with the right number of 50-lb bags.
What kind of sand goes in a pool filter?
#20 grade silica filter sand (0.45–0.55mm) only — not play sand, not paver sand. Wrong sand either channels (filters nothing) or blows through laterals into the pool. Glass media is a legit alternative at about 20% less weight for the same tank.
How often should filter sand be replaced?
Every 5–7 years typically. The tell: water never quite polishes clear, filter cycles between backwashes get shorter, and backwashing stops restoring pressure — the grains have worn round and smooth, so they stop grabbing.
How do I change filter sand without breaking the laterals?
Fill the tank a third with water first (cushions the laterals), pour slowly against a hand or plate to deflect, and cap the standpipe so sand can't fall inside it. Rushing this step is how a $30 sand change becomes a $150 lateral replacement.