Guide to Backwashing Your DE Pool Filter
Diatomaceous Earth (DE) is made of pulverized plankton fossils (called diatoms) that coat the filter element and acts as a filtration medium. This powder works with a specific type of filter that pushes the pool water through a set of grids. The grids get caked with the powder that collects impurities to keep the water in your inground pool or above-ground pool crystal clear and to help maintain your filter’s pressure.
Are you noticing cloudy or dirty pool water? Or are you seeing a pressure gauge reading 10 psi higher than normal? These are strong indicators that it’s time to “recharge” those grids by backwashing your DE filter to strip off the current power and replacing it with a new coat.
Backwashing a DE pool filter is the act of reversing the flow of water inside your filter tank. By changing the direction of the water, you can knock off the caked-on DE powder that has accumulated impurities from your pool water and flush it out. This will restore your filter to its highest efficiency to circulate your pool water and keep it healthy.
Did You Know?
During backwash, you can expect to replace about 4-6 pounds of DE powder. Make sure you have enough powder on hand before you start the process. If you don’t add enough new powder, the grids won’t be completely coated, and the dirt in your filter will attach itself right to the fabric on the grids and won’t backwash off. You’ll know when you’ve added enough new powder by checking the reading on the air pressure gauge. When the gauge hits its “normal” operational levels, stop adding powder.
When to Backwash a DE Pool Filter
You should backwash your DE pool filter about once a month during pool season. In addition to the regular schedule, you’ll want to perform additional backwashing if:
- You’ve been running your pool filter for 48 hours straight. This can cause a pressure build-up, even if the filter grids look clean.
- Higher-than-normal amounts of debris have entered your pool water. A heavy summer storm that washes sediment into your pool or a large potted plant that tips over into the pool can overtax the DE system.
- Your pool has had a heavy swimmer load for an extended period of time. If you’ve had houseguests for several days or your kids had friends over every day of the week, you’ll need to clear out the remnants from all the extra sunscreen, beauty products, and even sweat that will clog up your DE filter.
Pro tip: At least once during each pool season – and anytime your filter pressure remains high after backwashing – take the grids out of your DE filter and clean them more thoroughly.
How to Backwash a DE Pool Filter
Following a handful of easy steps for a standard three-cycle backwash is usually effective in keeping your DE filter clean:
Step 1: Turn off pool equipment.
Shut off the pump at the main power switch or, even better, at the circuit breaker box. Don’t change modes of operation on the valve with the pump on, or you can damage the spider gasket in the valve.
Step 2: Rotate the valve to the “Backwash” position.
For slide valves, turn backwash handle and pull the valve piston straight up to the backwash position. Lock it into position so it doesn’t slide up during operation. For multiport valves, push the handle down and rotate valve to the backwash position. Be sure the handle is pressed down all the way as you rotate it.
Step 3: Turn equipment back on and run the first cycle.
Turn the pump “in reverse” and run it for 1-3 minutes to strip the old DE powder and impurities off the filter grids. If you have a sight glass, you will see the water change from cloudy to clear as it flushes out.
Step 4: Turn the equipment off again.
Step 5: Rotate the valve to the "Rinse" position.
Step 6: Turn equipment back on and run the second cycle.
Switch the pump back on for about 30 seconds to rinse the grids from the “normal” filter side. The water will flow in the same as in “Filter” mode, except the water and any remaining impurities are purged out the waste line.
Step 7: Repeat steps 1-6 two more times.
Decrease the amount of backwash time to 30 seconds, then to 15 seconds. Repeating the cleaning cycle helps clear the really stubborn DE powder.
Step 8: Turn the equipment off again.
Step 9: Rotate the valve to the “Filter” position.
Step 10: Turn equipment back on and add new DE powder.
Add DE powder to the filter to replace the amount that was backwashed out. Uncover the skimmer closest to the pump and filter, and slowly pour the needed amount into the skimmer while the system is running. The powder will travel through the plumbing and effectively recharge the filter.