How to Backwash a Pool Filter

A man holds a pool filter.

Routine pool maintenance includes backwashing the pool filter. Most swimming pool filters use silica sand to filter and remove organic materials from your pool to keep the water clean. Backwashing the swimming pool filter removes built-up contaminants from the filter by reversing the flow of water through the filter and sending it out through a hose connected to the pump. Because backwashing the filter removes water from your pool, backwash your pool filter before adding any chemicals to the water.

Set the Pump to Backwash

Include backwashing your pool filter either as part of your weekly pool maintenance or when the pump gauge reads 8 to 10 psi. Before you change the setting on your pool pump, turn off the pump. Then, turn the handle on the pool pump to the backwash position. Once a month, or as needed, remove the clear lid from the filter and clean out the leaf basket. Rinse the basket and return it to the filter. Then, turn the pool pump on to begin backwashing.

Watch the Filter

Two women at a pool.

Depending on your pump, backwashing the pool filter takes 3 to 5 minutes to complete. Watch the pool filter through the clear lid. As the water flows backward through the filter, notice the particles swirling around. When the water inside the filter appears clear of particles, turn the pump off.

Rinse the Filter

With the pool pump off, turn the handle to rinse. Turn the pump back on and rinse the pool filter for 30 to 45 seconds. Rinsing the filter sends clean water through the pipes to wash away any leftover particles and prevent them from returning to the pool. It also settles the silica sand back to the bottom of the filter. After you rinse the filter, turn the pump off.

Filter the Water

A pool at nighttime.

Now that you’ve backwashed your pool filter, turn the handle back to the filter position and turn the pool pump back on. Refill the pool to the proper level with fresh water and add any needed chemicals.

Backwash the pool filter regularly to maintain your pool filter at peak performance and to keep your swimming pool clean.