How to Backwash Your Sand Filter

Sand filters are typically the low-maintenance pool filter. There aren’t any grids or media that need periodically cleaned, and the sand can last almost 5 years without replacing.

The one thing you do need to perform is a backwashing. As the sand inside traps dirt, oils, and other debris, the filter clogs up and puts stress on your pump. A backwash releases that debris and cleans out the filter.

The process of backwashing your sand filter is fairly easy, you’ll just need to know when the right time is to do it.

When A Sand Filter Needs a Backwash

Unlike other filters, sand actually works slightly better when it’s a little bit dirty. The trapped debris helps catch even smaller particles. But, there is a point when it gets too dirty.

Look out for these signs to determine when a backwash is necessary:

• PSI is 25% above normal pressure. At the start of the season, you should get in the habit of remembering your “clean” PSI on the filter. This is the pressure reading when the filter is first turned on. A good rule to follow is to clean out your filter when your pressure is about 25% above normal PSI levels.
• Weak return flow of water: If the water coming out of the return jets isn’t as strong as they normally are, there is a high chance your filter is holding too much debris.
• Post-algae shock treatment. If you’ve just finished a shock treatment and have been vacuuming up a dead algae bloom, you should backwash to get that algae out of the filter.

Steps to Backwashing a Sand Filter

Follow these steps for a simple backwash. Note that this is following a sand filter that utilizes a multiport valve.

1. Attach a backwash hose if you have one. If your sand filter has a waste or backwash port, attach a hose so the dirty water can flow farther away from your equipment.
2. Turn off the pump. You can either shut the main power switch from the pump or, even better, at the circuit breaker box itself.
3. Set the valve to BACKWASH. This setting reverses water flow, forcing it to go backwards into the filter. Water will shoot out of a waste port.
4. Turn the pump back on to start the first cycle. Run the pump for about a minute. If you have a sight glass, run it until the glass is “clear”.
5. Turn off the pump.
6. Set the valve to RINSE. This setting removes sediment and dirt caused by the backwash.
7. Turn the pump back on. Run the pump on RINSE for about 30 seconds.
8. Turn off the pump.
9. Repeat steps 3-8 two or three more times. This will guarantee the majority of the heavy dirt and debris has been moved out of the filter.
10. Turn off the pump.
11. Set valve to FILTER and turn the pump back on.

After the backwash is complete, you do not need to add more sand to the filter. While a tiny bit of sand may escape through the waste line, it isn’t enough to make a difference.

Good as New!

Backwashing is an easy, but necessary, pool maintenance item. Five minutes of your time can get your filter back to running normal again.

Now it’s time to get back to what really matters, and that’s enjoying the pool!