Drain the filter tank completely before you touch the sand

Turn off the pump and close the multiport valve on top of the filter. Open the drain plug at the bottom of the tank — usually a large plastic bolt on the side or underside — and let all the water run out into a bucket or onto the ground. This step takes 10 to 20 minutes depending on tank size. Do not skip it: wet sand is heavy and messy, and water pressure inside the tank can spray sand everywhere when you open the top.

Once the tank is empty, open the top of the filter. Most residential filters have a large bolt or clamp ring that holds the lid down. Use a wrench to loosen it, then unscrew by hand. Set the lid aside in a clean spot — you will need to reseal it later.

Key Takeaways

  • Drain the tank completely and turn off the pump before opening the filter, or you risk water and sand spraying out under pressure.
  • Remove the multiport valve assembly at the top of the tank so you can access the sand underneath without damaging the valve.
  • Scoop out the old sand carefully and dispose of it, then rinse the tank bottom to remove fine particles and debris.
  • Pour in new pool filter sand in the correct grade (usually 20-grade silica sand) and refill the tank with water before restarting the pump.
  • Run the filter on backwash for 3 to 5 minutes after refilling to settle the sand and clear cloudy water from the tank.

Remove the multiport valve to access the sand

The multiport valve sits on top of the filter and controls water flow. You must remove it to reach the sand below. Close the isolation valve on the pipe leading into the multiport valve, then unbolt the valve from the tank. Most valves are held down by four to six bolts around the perimeter. Use a wrench to remove them one at a time, working in a cross pattern so the valve comes off evenly.

Once the bolts are loose, lift the valve straight up and set it on a clean surface. You may see a rubber gasket or O-ring underneath — keep this in place or set it aside carefully, as you will need it when you reassemble. Some filters have a standpipe (a vertical tube) that runs down into the sand; if yours does, note how deep it sits so you can reinstall it at the same depth.

Scoop out the old sand and rinse the tank

Use a plastic scoop or small shovel to remove the old sand. Work from the edges toward the center, and scoop carefully so you do not damage the lateral pipes at the bottom of the tank — these are the curved pipes with small slots that collect filtered water. If you see cracks in the laterals or sand that has compacted into hard clumps, the laterals may need replacement, but that is a separate job.

Once the sand is out, rinse the inside of the tank with a garden hose. Spray the bottom and sides to remove fine sand particles and debris. Let the water drain out through the drain plug. Repeat the rinse two or three times until the water runs mostly clear. This step prevents old sand from mixing with new sand and clogging the filter faster.

Pour in new pool filter sand at the correct grade

Pool filters use silica sand in a specific grade, usually 20-grade or 16-grade. Check your filter manual or the label on your old sand bag to find the right grade for your model. Do not use play sand, sandbox sand, or any other type — these grades are too fine and will clog the filter or pass through into the pool.

If your filter has a standpipe, reinstall it first at the same depth it was before. Then pour the new sand slowly into the tank. Most residential filters hold 100 to 300 pounds of sand depending on size. Spread the sand evenly across the bottom as you pour so it settles in a level layer. Avoid dumping all the sand in one spot, which can shift the standpipe or damage the laterals.

Refill the tank and run the backwash cycle

Once the sand is in place, reinstall the multiport valve. Make sure the gasket or O-ring is seated properly, then bolt the valve back down using the same cross pattern you used to remove it. Tighten the bolts firmly but do not over-tighten, which can crack the tank.

Close the drain plug and open the isolation valve on the intake pipe. Turn the multiport valve to the "Fill" or "Rinse" position, then turn on the pump. Fill the tank slowly — this lets the sand settle and prevents air pockets. Watch the sight glass (the clear tube on the side of the tank) to see the water level rise. Fill until the water reaches the top of the sand or the level marked on your tank.

Once full, turn off the pump and switch the multiport valve to "Backwash." Turn the pump back on and run it for 3 to 5 minutes. You will see dirty water and air bubbles come out of the backwash line. This cycle settles the sand and clears fine particles. When the water runs clear, turn off the pump, switch the valve back to "Filter," and restart the pump. The pool should begin filtering normally.

Check water clarity and pressure after replacement

The pool water may look cloudy for a few hours after you restart the filter. This is normal — the new sand is still settling. Run the filter continuously for at least 8 to 12 hours, or overnight if possible. Check the pressure gauge on the filter; it should read between 10 and 20 PSI depending on your model. If the pressure is much higher, run another backwash cycle.

If the water stays cloudy after 24 hours, or if the pressure climbs above 25 PSI, the sand may have been installed unevenly or the laterals may be damaged. Turn off the pump, drain the tank again, and check that the sand is level and the standpipe is straight. If the laterals are cracked, they will need to be replaced before the filter can work properly.

How often to replace pool filter sand

Pool filter sand typically lasts 3 to 5 years before it becomes too compacted or clogged to filter effectively. You will notice the pressure gauge climbing faster than usual, or the water staying cloudy even after the filter runs for hours. Some pool owners backwash weekly or after heavy use, which extends sand life by breaking up compaction. If you backwash regularly and rinse the filter once a year, you may get 5 to 7 years from a single batch of sand.

Keep a record of when you replaced the sand so you know when to plan the next replacement. Sand is inexpensive — usually 20 to 50 dollars per bag — so replacing it on schedule is much cheaper than running a clogged filter or replacing damaged laterals.

Frequently Asked Questions

Can I reuse the old sand if I rinse it well?

No. Old sand becomes compacted and coated with algae, minerals, and debris that rinsing cannot remove. Reusing it will clog faster and filter less effectively than new sand. Dispose of old sand in the trash or at a yard waste facility.

What if I do not know what grade of sand my filter uses?

Check the manual that came with your filter, or look at the label on the side of the tank. If you cannot find either, contact the filter manufacturer with your model number. Using the wrong grade will damage the filter or let debris into the pool, so it is worth confirming before you buy.

How do I know if the laterals are broken?

If water leaks from the drain plug when the pump is off, or if sand comes out of the return line into the pool, the laterals are cracked. You can also drain the tank and look at the bottom — the laterals are the curved pipes with slots. If you see cracks or loose pieces, they need replacement.

Do I need to add chemicals after replacing the sand?

No. Replacing sand does not change the chemistry of the pool water. Test the water after the filter has run for 24 hours and adjust chemicals as you normally would based on the test results.

Why is the pressure gauge so high right after I refill?

New sand is denser and more tightly packed than aged sand. The pressure will drop slightly over the first few days as the sand settles. If it stays above 25 PSI after a week, run another backwash cycle or check that the sand is level inside the tank.