Diatomaceous Earth for Pool Filters: How Do They Work?

A Comprehensive Guide to Diatomaceous Earth (DE) Pool Filter Systems

Understanding your swimming pool's equipment is crucial for maintaining a clean and healthy pool. It’s not just about knowing when to call for repairs or order new parts—it’s about knowing how the equipment works. There are three main types of pool filters: diatomaceous earth (DE), sand, and cartridge filters. In this guide, we'll focus on DE filters and explain how they work, how to maintain them, and how to troubleshoot common issues.

How DE Filter Systems Work

Among the three types of filters, DE pool filter systems are often considered the most efficient due to their superior filtration capability, with a micron rating of 1 to 3 microns. This means DE filters can trap even the tiniest particles, keeping your pool water exceptionally clear.

DE filters use a fine powder made from the fossilized remains of diatoms, a type of algae. When added to the filter, the powder coats a grid, creating a barrier that captures dirt and debris as water passes through. The result is cleaner, clearer water.

It’s important to monitor the pressure gauge on your DE pool filter system regularly. A rise in pressure indicates that the filter is becoming clogged with debris and needs to be backwashed. Typically, backwashing is necessary when the gauge reads 8-10 pounds above the clean pressure.

How to Backwash a DE Filter System

Backwashing is the process of cleaning the DE filter by reversing the water flow to flush out the trapped debris. There are two methods to backwash a DE filter: using a side valve or a multiport valve.

Backwashing with a Side Valve

1. Turn Off the Filter: Start by switching off the filter and, if applicable, attach your backwash hose.
2. Unlock the Plunger: Pull the plunger up about three inches.
3. Open the Air Bleeder and Start the Pump: With the plunger up, open the air bleeder, and turn the pump on. Run the pump until the water in the hose runs clear (about two minutes).
4. Rinse and Repeat: Turn off the pump, reset the plunger, and repeat the backwashing process three times.
5. Add DE Powder: After the final rinse, turn the pump on at a low pressure and add the DE powder. Keep an eye on the pressure throughout.

Backwashing with a Multiport Valve

1. Turn Off the Filter: Begin by turning off the filter and switching the valve from “filter” to “backwash.”
2. Attach the Backwash Hose: If you have a hose, attach it; otherwise, open the waste valves.
3. Open the Air Bleeder and Start the Pump: Once the hose fills with water, let the pump run until the water is clear (about three minutes).
4. Rinse: Turn off the pump, set the valve to “rinse,” and run for 10 seconds.
5. Repeat: Switch back to “backwash” and repeat the process three times.
6. Add DE Powder: Finally, return the valve to “filter” and add DE powder before turning the system back on. Monitor the pressure during this process.

Troubleshooting DE Filter Systems

Regular checks are essential to ensure your DE pool filter operates smoothly throughout the swimming season. If your filter becomes clogged, turn off the system and remove the filter grid for cleaning. Rinse the grid thoroughly and soak it in a cleaning solution.

If your pool water becomes cloudy despite a clean filter, it may be due to insufficient filtration time. The duration your filter should run each day depends on the size and age of your filter system. Older systems may need to run longer, while newer systems can operate efficiently with shorter run times.

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