Drain the filter tank completely before you start

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 or metal valve — 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 harder to remove, and water pressure can make the job unsafe.

Once the tank is empty, open the air relief valve at the top to break the seal and let air in. This makes it easier to remove the old sand. Leave both the drain plug and air relief open while you work.

Key Takeaways

  • Drain all water from the tank and open both the drain plug and air relief valve before touching the sand.
  • Remove old sand by hand or with a wet/dry vacuum, working in layers from the top down.
  • Rinse new sand in a bucket before adding it to the tank to remove dust and prevent cloudy water.
  • Fill the tank with water slowly while adding sand in the correct layers — gravel first, then sand — to avoid settling and shifting.
  • Run the filter in backwash mode for 3 to 5 minutes after refilling to clear trapped air and dust.

Remove the old sand layer by layer

Scoop out the sand by hand using a small bucket or shovel, or use a wet/dry vacuum if you have one. Work from the top down in layers. Most filters have a standpipe (a tube running down the center) that you need to protect — do not let the shovel hit it or you will crack it. If the standpipe has a cap or diffuser on top, remove it first and set it aside.

Sand removal is dusty work. Wear a dust mask and do it outside or in a garage with the door open. A standard pool filter holds 100 to 300 pounds of sand depending on the model, so expect this to take 30 to 45 minutes. Once the tank is empty, wipe the inside walls with a damp cloth to remove any remaining dust.

Rinse the new sand before it goes in the tank

New pool filter sand comes with a fine dust coating that will cloud your pool water if you add it dry. Fill a 5-gallon bucket with water, pour in a few shovels of sand, stir it hard for 30 seconds, and pour off the cloudy water. Repeat this 3 to 4 times until the water runs mostly clear. This takes about 10 minutes but saves you from having to backwash for hours afterward.

If you are replacing a large filter, you can speed this up by rinsing sand in a wheelbarrow with a garden hose, stirring as you spray. The goal is to remove the dust without losing the sand itself.

Add gravel and sand in the correct order

Most pool filters need two layers: a bottom layer of gravel (also called support media) and a top layer of sand. Check your filter manual or the label on the side of the tank to confirm the exact depth for each layer — this varies by model. A common setup is 6 inches of gravel followed by 18 inches of sand, but yours may differ.

Start by adding the gravel layer. Pour it slowly into the tank and spread it evenly across the bottom. Then add the rinsed sand on top, pouring it slowly and smoothing it out as you go. Do not pack it down — the sand needs to settle naturally once water is added. If you have a standpipe, make sure it stays centered and upright as you add material around it.

Fill the tank with water slowly and carefully

Once the sand and gravel are in place, reinstall the diffuser or cap on top of the standpipe if your filter has one. Close the drain plug and air relief valve. Now turn on the pump and fill the tank with water very slowly — use a garden hose on low flow or a bucket-and-pour method. Filling too fast can shift the sand layers and create air pockets.

As the water level rises, watch for the sand to settle. It will drop an inch or two as air escapes and the material compacts. Keep filling until the water reaches the normal operating level marked on the tank, usually about three-quarters full. This process takes 20 to 30 minutes.

Run backwash to clear air and dust from the system

Once the tank is full, turn off the pump. Set the multiport valve to the backwash position and turn the pump back on. Run it in backwash mode for 3 to 5 minutes. You will see dirty water flow out the waste line — this is normal and expected. The backwash clears trapped air bubbles and any remaining dust from the new sand.

After backwashing, turn off the pump again, switch the multiport valve back to the filter position, and turn the pump on one more time. Let it run for 1 to 2 minutes, then turn it off. Your filter is now ready to use. The water in your pool may be slightly cloudy for a few hours as any remaining fine particles settle, but it will clear on its own.

Check the pressure gauge and monitor for leaks

Before you close up, look at the pressure gauge on top of the filter. It should read between 10 and 20 PSI when the filter is clean and running. If it reads much higher, the sand may be packed too tightly or the layers may be reversed. If it reads much lower, you may have an air leak or the sand may not be settled yet — run the filter for another hour and check again.

Watch the drain plug and air relief valve for any leaks while the pump runs. A small drip is normal during the first few minutes as air escapes, but a steady stream means the tank seal is damaged and you may need to replace the tank itself. If everything looks dry after 10 minutes of running, you are done.

Frequently Asked Questions

How often do I need to replace the sand in my pool filter?

Most pool sand lasts 3 to 5 years before it breaks down into fine particles and stops filtering well. You will notice the pressure gauge climbing faster than usual, or the water staying cloudy even after backwashing. When that happens, it is time to replace it. Some filters need sand replaced sooner if the pool is heavily used or if you do not backwash regularly.

Can I reuse the old sand or do I have to buy new?

Old pool filter sand cannot be reused in the same filter because it has broken down into smaller particles and lost its filtering ability. You can sometimes use it in a sandbox or garden, but not back in the pool filter. Buy new sand rated for pool filters — it is usually labeled as silica sand or pool filter sand and costs between $15 and $40 per 50-pound bag depending on where you buy it.

What if water leaks out the sides of the tank while I am filling it?

Stop filling when ready and turn off the pump. Check the drain plug and air relief valve to make sure both are fully closed. If they are closed and water is still leaking, the tank itself may be cracked. Drain it completely and inspect the walls and seams for damage. A cracked tank cannot be repaired and will need to be replaced.

Do I need to backwash before I use the pool after replacing the sand?

Yes. Even after the initial backwash during setup, run the filter in backwash mode for another 2 to 3 minutes before you swim. This clears any remaining dust that settled during the first few hours. Your pool water should be clear and the pressure gauge should be stable before you consider the job complete.

What is the difference between pool sand and regular sandbox sand?

Pool filter sand is graded to a specific particle size (usually 0.45 to 0.55 millimeters) so it filters water effectively without letting debris through. Sandbox sand is much finer and will clog your filter or pass right through without filtering anything. Always buy sand labeled for pool filters, not general-purpose sand.