EQUIPMENT
Backwashing the sand filter
Backwash when the gauge sits 8–10 psi above its clean reading: switch the pump off before you move the valve, then run it until the sight glass runs clear, usually two to three minutes.
Backwashing reverses the flow up through the sand so the dirt it has trapped goes out of the waste line. Do it only when it is needed — backwashing too often never lets the bed settle into a good filtering layer, and wastes water for nothing.
Read the gauge. If it is not yet 8–10 psi above the clean figure, it does not need backwashing.
Switch the pump off at its switch and wait for it to stop completely.
Check the waste hose ends somewhere the water can actually go.
Press the valve handle down and turn it to BACKWASH, letting it spring fully into its notch.
Start the pump and watch the sight glass. Keep going until the water runs clear — normally 2–3 minutes.
Switch off, turn the valve to RINSE and run for 30–60 seconds. This resettles the sand bed; skip it and you blow sand back into the pool.
Switch off, return the valve to FILTER, and restart.
Write down the new gauge reading. That is the clean-filter figure you will compare against next time.
Top the pool back up to the middle of the skimmer. One backwash uses several hundred litres and the drop is easy to see.
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