Seasonal & DIY

How to Backwash a Pool Filter

Backwashing too often wastes water and filter media life; backwashing too rarely lets a clogged filter choke circulation, and the pressure gauge is what tells the difference. The Woodlands Township Covenants require Design Review Committee approval for pool and backyard construction in nearly every village, and that review covers fencing, setbacks, and drainage as well as the pool itself.

Custom gunite pool and raised spa with stone hardscape

Backwashing reverses water flow through a sand or DE filter to flush trapped debris out to waste, resetting the filter's effectiveness.

Note the clean, just-backwashed pressure
Record the filter pressure gauge reading right after a backwash while the filter is freshly clean; this becomes the baseline to compare against going forward.
Backwash when pressure rises 8-10 psi above baseline
That rise indicates the filter media is loaded with trapped debris and restricting flow enough to matter, the correct trigger point rather than a fixed calendar schedule.
Turn off the pump before changing valve position
Changing a multiport valve or push-pull valve while the pump is running can damage the valve; always shut the system down first.
Set the valve to backwash and restart the pump
Run until the waste-line water runs clear, typically a couple of minutes, watching through a sight glass if the system has one.
Rinse before returning to filter mode
A short rinse cycle after backwashing (on systems with that setting) settles the media bed and prevents cloudy water from flowing straight back into the pool.
Recharge DE filters with fresh powder
DE filters specifically need fresh diatomaceous earth added through the skimmer after backwashing, since the backwash process flushes out the old DE coating along with the trapped debris.