Backwashing a sand filter is a simple process to clean it by reversing the water flow, sending trapped debris out of the filter and away from the pool.
To backwash your pool sand filter, you need to reverse the water flow through the filter media. This lifts the accumulated debris off the sand and flushes it out through a waste line. This process restores the filter's efficiency and helps maintain clear, healthy pool water.
Steps for Backwashing a Sand Filter
Based on standard pool maintenance procedures, including the steps outlined in the reference provided (Hornsby Pool Care), here is how to backwash your sand filter:
- Turn off the pool pump. This is a crucial safety step to prevent damage to the valve or filter. Always turn off the pump before changing the filter valve position.
- Set the filter valve handle to the 'Backwash' position and ensure the handle locks in place. Your filter's multiport valve will have different settings like 'Filter', 'Backwash', 'Rinse', 'Waste', 'Closed', and potentially 'Recirculate'. Locate the 'Backwash' setting and move the handle firmly into that position.
- Turn the pump on and backwash for 3-5 minutes or until the water in the sight glass (located on the filter) is running clear. Once the pump is on, water will flow backwards through the filter bed and exit through the waste port. Most filters have a small transparent sight glass near the valve where you can observe the water color. Initially, it will likely be cloudy or discolored with debris, but it should clear up as the backwashing progresses.
When to Backwash
You should backwash your sand filter when:
- The pressure gauge on your filter reads 8-10 PSI (pounds per square inch) higher than its clean operating pressure. This indicates the filter is becoming clogged with debris.
- You notice a decrease in water flow back to the pool.
- The pool water is not as clear as usual, despite proper chemical balance.
- Regularly, as part of your pool maintenance schedule (e.g., every 1-2 weeks during peak season).
What's Next? Rinse!
After backwashing, it is essential to perform a 'Rinse' cycle. The backwash process can leave the sand bed uneven. Rinsing settles the sand and flushes out any remaining cloudy water from the backwash line before returning to filtering the pool water.
- Turn the pump off again.
- Set the valve handle to the 'Rinse' position.
- Turn the pump on and rinse for about 30-60 seconds, or until the water in the sight glass runs clear again.
- Turn the pump off.
- Set the valve handle back to the 'Filter' position.
- Turn the pump back on to resume normal filtration.
Performing regular backwashing followed by rinsing is key to keeping your sand filter working efficiently and your pool water sparkling clean.
Understanding Filter Valve Positions
Most multiport filter valves have common positions:
| Position | Function | Pump Status |
|---|---|---|
| Filter | Normal filtering of pool water | On |
| Backwash | Cleans the filter media by reversing flow | On (during cycle) |
| Rinse | Settles filter media after backwashing | On (during cycle) |
| Waste | Drains water directly out (bypassing filter) | On |
| Closed | Shuts off all flow to the filter and pool lines | Off |
| Recirculate | Bypasses the filter, circulating water only | On |
Always ensure the pump is off before changing the valve position to avoid damaging the valve's internal components.
