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What is pool filter sand? #20 silica, explained

Pool filter sand is washed silica sand screened to a narrow grain size, usually sold as #20 grade. That narrow size is the whole point: it packs into a bed with gaps small enough to catch dirt and big enough for water to pass.

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Updated October 12, 2026Research based, not hands-on testing

#20 SILICA SANDAngular quartz grainsNarrow size rangeThe default media formost sand filters0.45 to 0.55 mm
Fig. 1 #20 silica grains, magnified. The grade means a narrow size range, roughly 0.45 to 0.55 mm.

Short answer

Pool filter sand is #20 grade silica sand: washed quartz grains screened to about 0.45 to 0.55 mm. Hayward’s S200 manual calls it “No. 20 or No. 1/2 silica sand.” The uniform size lets water flow evenly through the bed while dirt gets caught in the spaces between grains. Play sand and all-purpose sand are finer and mixed, so they clog and can pass into the pool.

What makes it pool filter sand

How a sand filter uses it

PRESSURE GAUGEMULTIPORT VALVEDIFFUSERWATER IN#20 SILICA SANDSTANDPIPELATERALSDRAIN PLUG
Fig. 2 Water comes in through the diffuser at the top, passes down through the sand bed, and leaves through slotted laterals at the bottom. Dirt stays in the sand.

The pump pushes pool water into the top of the tank. It spreads out over the sand, trickles down through the bed, and leaves through slotted arms at the bottom called laterals. Dirt gets trapped in the spaces between grains. As the bed fills with dirt, the pressure gauge climbs, and you clean it by backwashing: running water up through the bed and out to waste.

The narrow grade matters for both jobs. Uniform grains leave even gaps for water, and they are heavy enough to settle back after a backwash without washing out to waste.

The grade, in numbers

SourceGradeGrain size
Hayward S200 manualNo. 20 or No. 1/2 silica0.45 to 0.55 mm
Quikrete No. 1153US sieve #20 to 400.85 to 0.425 mm
HTH 50 lb (retailer listing)20 grade0.45 to 0.55 mm
Pentair Triton IIStandard #20 silicanot listed
Intex SX2800#20 silicanot listed

Sand you should not use

Play sand, masonry sand, all-purpose sand and beach sand look similar but are finer and mixed in size. Fine grains fill the gaps in the bed, so pressure climbs fast, and the smallest grains can pass through the laterals and end up in the pool. See play sand vs pool filter sand.

POOL FILTER SAND#20 grade, narrow sizePLAY SANDfiner, mixed sizes
Fig. 3 Pool filter sand is coarse and uniform. Play sand is finer and mixed, which packs the bed tight.

How long it lasts

The grains wear smoother over the years and the bed collects oils and scale. Intex says to replace the sand every 5 years in its pumps; Inyo Pools suggests 5 to 7 years for inground filters. The signs to watch are in how often to change pool filter sand.

See #20 pool filter sand on Amazon

Questions people ask

What does #20 mean on pool filter sand?

It refers to the grain size the sand is screened to, named after the sieve sizes used to grade it. Hayward lists #20 filter sand at 0.45 to 0.55 mm. Quikrete grades its pool filter sand between US sieve #20 and #40, 0.85 to 0.425 mm.

Is pool filter sand the same as silica sand?

Pool filter sand is a silica sand, but not every silica sand is pool filter sand. Silica sand is sold in many grades for sandblasting, glass making and landscaping. For a pool filter you need the grade the filter maker lists, usually #20.

How small a particle does sand filter out?

Sand filters catch fine dirt in the spaces between grains, and the bed gets better at it as it loads with dirt, until the pressure rises and it is time to backwash. Published micron figures vary by source, so we do not quote one; makers of glass and zeolite claim finer filtering than sand.

Can I use pool filter sand for other things?

People use it for paver joints, sandboxes and aquariums, but those are not what it is sold for. If you do, remember the bag is fine crystalline silica and the dust warning still applies.

Sources

  1. Hayward S200 high-rate sand filter owner’s manual (maker PDF, hosted by The Pool Factory)
  2. Quikrete Pool Filter Sand No. 1153 data sheet (maker PDF)
  3. Hemlock Hardware, HTH 50 lb Pool Filter Sand listing (retailer)
  4. Pentair Triton II fiberglass sand filter brochure (maker PDF, hosted by propools.com)
  5. Intex SX2800 14 in Krystal Clear sand filter pump, specifications (maker)
  6. Inyo Pools, How to replace the sand in a Pentair Triton II side valve sand filter

Last reviewed October 12, 2026. Sand amounts and listings change; check your filter’s label or manual before you buy, and follow the maker’s instructions.

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