Pool filter sand is not a forever material. Over five to seven years, the sharp silica grains that trap particles become rounded, smooth, and ineffective. The filter still looks full of sand, so many owners — and some techs — miss the replacement window entirely. Cloudy water that does not clear despite correct chemistry, a filter that requires backwashing every few days instead of every few weeks, and pressure that climbs unusually fast are all signs the sand is spent.
Standard pool filter sand is #20 silica sand with a grain size between 0.45 and 0.55 mm. This specific size is chosen because the irregular particle shape and size create tortuous paths that trap contaminants in the 20-micron range. Hardware store sand — play sand, masonry sand, washed river sand — has different grain distributions and will either clog rapidly or allow particles to pass through.
Two upgrades are increasingly popular on service routes:
For commercial pools with heavy bather loads, filter glass pays for itself in reduced chemical demand and less frequent backwashing within two seasons.
Turn off the pump and close all valves. Set the multiport valve to the "closed" or "winterize" position so water does not flow during the work. Have a shop vac, buckets or tarps, and your new sand ready before you open the tank.
The fastest method: use a wet/dry shop vac. Remove the multiport valve from the top of the tank. Insert the shop vac hose into the sand and work in sections, emptying the vac into a wheelbarrow or trash bags as you go. An average residential tank has 150–350 lbs of sand — plan for 45–60 minutes of extraction.
Do not try to dump the tank on its side. On older tanks with aging laterals, the lateral assembly can shear off, leaving you with a much larger repair than a sand change.
Once the tank is empty, shine a flashlight into the bottom and inspect every lateral — the finger-like distribution tubes radiating from the center standpipe. Look for cracks, missing end caps, and broken sections. A single cracked lateral sends sand back to the pool. Replace any damaged laterals before adding new sand.
Fill the tank halfway with water before adding sand — this cushions the laterals from the weight of sand dropping in. Pour sand slowly through the top opening, keeping the standpipe centered. Fill to the manufacturer's specified level, typically about two-thirds full — never to the top.
Reinstall the multiport valve. Set it to BACKWASH and run for 3–5 minutes to flush fine particles from the new sand. Then switch to RINSE for 30 seconds to settle the bed. Switch to FILTER and resume normal operation. Expect slightly elevated pressure for the first day or two as the sand bed settles and compacts.
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Open SplashLens Free →Filter tank size determines sand load. A typical residential 24-inch tank takes 200 lbs, a 26-inch takes 250 lbs, and a 30-inch takes 350 lbs. Always check the manufacturer spec for your exact model — overfilling prevents backwash from working correctly.
No. Pool filter sand is #20 silica sand with a specific grain size of 0.45 to 0.55 mm. Play sand, masonry sand, and all-purpose sand have different particle sizes that clog quickly or allow fine particles to pass through.
Filter glass (crushed recycled glass) filters down to about 5 microns vs sand at 20 microns, is more resistant to channeling, and lasts longer. The trade-off is cost — it is typically 3–4x the price of sand. For commercial or high-demand pools, the performance gain is worth it.
Spent pool filter sand is safe for landfill disposal. Many landscapers use it as fill material. Do not use it in children's play areas as it may contain chemical residue from years of chlorination.