How to Backwash a Pool Filter

Step 1

Turn Off the Pump

Always turn off the pool pump before adjusting the filter valve to avoid damage to the system.

Step 2

Set the Filter Valve to “Backwash”

For a multiport valve: Turn the valve handle to the “Backwash” position.
For a slide valve: Pull the handle upward to initiate the backwash mode.

Step 3

Attach a Backwash Hose

If the backwash hose isn’t already connected to the filter valve’s waste line, attach it now.
Screw a hose fitting into the waste line, slide the hose onto the fitting, and secure it with a saddle clamp.
Unroll the hose completely to a proper drainage area. Leaving the hose rolled up can cause it to burst.

Backwash Filter Hose - DIY Pool Resources - INYOPools.com

Step 4

Turn On the Pump

Restart the pool pump and let it run for 2-3 minutes or until the water in the backwash sight glass (if equipped) runs clear.

Step 5

Turn Off the Pump Again

Shut off the pump once the backwash cycle is complete.

Step 6

Set the Valve to “Rinse” (Sand Filters Only)

Turn the multiport valve to “Rinse” to settle the sand back into place and prevent debris from re-entering the pool.
Run the pump for 30 seconds to 1 minute.
Turn off the pump again.

Step 7

Return the Valve to “Filter” Mode

After completing the backwash and rinse cycles, set the valve back to “Filter” mode.

Step 8

Restart the Pump

Turn the pump back on to resume normal filtration.

Step 9

Additional Steps for DE Filters

After backwashing a DE filter, new DE powder must be added to the filter to maintain its filtration efficiency.
Determine the correct amount of DE powder required by consulting your filter’s manual (typically measured in pounds or scoops).
Add the DE powder to the pool skimmer while the pump is running to allow it to coat the filter grids evenly.

Key Differences Between Sand and DE Filters

Sand Filters:

Media Type: Use sand to trap debris.
Backwashing Frequency: Typically every 1-2 weeks or when the pressure gauge reads 8-10 psi above the clean pressure level.
Post-Backwash Rinse: Requires a rinse cycle to resettle the sand bed.
No Additional Media Needed: Once backwashing is complete, you’re ready to resume filtration without adding new material.

DE Filters:

Media Type: Use diatomaceous earth powder to coat grids and capture debris.
Backwashing Frequency: Typically every 4-6 weeks or when the pressure gauge reads 8-10 psi above the clean pressure level.
Post-Backwash Media Replacement: Requires adding new DE powder to the skimmer after each backwash to coat the grids.
Maintenance: DE grids may need periodic cleaning or replacement.

Tips for Effective Backwashing

Monitor the Pressure Gauge: Always backwash when the pressure gauge shows an increase of 8-10 psi above normal.
Avoid Over-Backwashing: Excessive backwashing can waste water and affect filtration efficiency.
Dispose of Wastewater Properly: Ensure the backwash hose directs wastewater to a safe location per local regulations.
Keep DE Powder on Hand: If you have a DE filter, stock up on DE powder to avoid interruptions in maintenance.