How to clean a DE pool filter

It’s important to know how to clean a DE pool filter as it’s part of keeping your pool clean, keeping your system running efficiently, and making sure your filter is picking up and filtering the debris running through it properly. Pool filters come in many different shapes and sizes, and some are more efficient (and more expensive) than others. 

But all pool filters use the same basic principle: water pumped through your pool’s circulatory system runs through a filter medium, usually built into a tank next to the pump, to catch and filter small debris, algae, and organic material, that would otherwise pass through your pool skimmer basket. 

Most pool filters are either cartridge filters, sand filters, or DE (diatomaceous earth) filters

What is a DE pool filter?

Diatomaceous earth filters, or DE pool filters, utilize extraordinarily fine powder called diatomaceous earth to filter your pool. This powder is caked onto a filter grid assembly, made of fine plastic fibers. 

DE is finer than sand, and filters much more thoroughly than cartridge filters. However, DE filters have to be cleaned 2 – 4 times per year, and the DE needs to be reapplied. On the other hand, maintenance for a DE pool filter isn’t all that troublesome. 

To make the most of your DE pool filter, you must treat it right. And that means cleaning the filter with a backwash in between full cleanings, replacing soiled DE powder, and inspecting the grid assembly after each filter clean.

How DE pool filters work

DE pool filters are capable of filtering particles as small as 3-5 microns. For comparison, a fine grain of sand is about 125 microns. Human hair is about 50 microns wide. The naked eye can only see objects with a minimum micron size of 35. 

What this means is that if you’re working with a diatomaceous earth filter, your pool water is going to be about as well-filtered as it can possibly get. 

DE powder is made from the fossilized remains of single-celled algae called diatoms, whose cell walls are made of a transparent silica. The DE powder used as a filter medium is not to be confused with the DE powder often sold for pest control. It is produced differently and serves a different function. One alternative that most pool professionals use is AquaPerl. AquaPerl is used the same way as DE but is a DE replacement. It is all natural, not harmful to the environment, and is not a carcinogen like DE is.

The DE powder itself is packed tightly onto multiple grids made of frames with plastic fiber. The powder is soiled over time by minerals and oils, as well as organic particles. Because all the powder is caked to the grids on one side, cleaning them is usually as simple as just letting the pump backwash over the grids, using the water pressure to knock the soiled powder off the assembly, and flushing it away. 

It’s critical to know that there are regulations around the disposal of DE powder. Make sure to check with your municipality before you get yourself fined for backwashing DE powder into the town water grid. The powder itself is a noted carcinogen, although not necessarily to humans. To be safe, wear a qualitative protective mask when working with DE powder and keep it far away from pets and children.

Backwashing your DE pool filter

Most pool pumps outfitted with DE pool filters are cleaned through a simple backwash. This reverses the flow of water in the filter and knocks the powder off the grid. It’s a simple step-by-step procedure: 

  1. Turn off all pool equipment (especially the pump).
  2. Set the valve to backwash.
  3. Turn your pump back on and run it for a few minutes.
  4. Shut it back off and set the valve to filter.
  5. Turn it back on and add DE powder directly into the skimmer.

To figure out exactly how much powder to add, consult your filter’s owner’s manual. The exact amount per backwash depends on how long you backwashed the filter, and how large your filter is.

How often should you backwash your DE pool filter?

As a general rule of thumb, you should backwash your DE pool filter one to two times in between filter cleans. However, it helps to be a conscientious pool owner, and learn to diagnose a clogged filter by keeping an eye on your pool filter’s water pressure. 

You should keep an eye on what pressure your filter reads when it’s fresh and clean and take note of it. The higher the pressure goes, the closer the filter is to a backwash. If your filter regularly records about 20psi after being cleaned, then wait for your water pressure to kick up to about 30psi to do a backwash.

Deep cleaning a DE filter

The simplest way to deep clean a filter is to hose down the grid. Doing so can also help you find a potentially broken grid and replace it. To deep clean a DE filter, simply: 

  1. Remove the filter drain plug.
  2. Open your filter. 
  3. Hose your filter down.
  4. Carefully remove the grid assembly. 
  5. Spray between the grids for a deep clean.
  6. Replace the grid assembly. 

Be careful when handling the grid assembly. Deep cleans are only going to be necessary a few times over the course of the filter’s life cycle, at a rate of about once every six months.

Consider a chemical clean

Hosing off the grids will get most of the job done, but there are ways to get an even more thorough clean on an older DE filter. Oil and mineral deposits can clog the grids over time, and water pressure from a hose usually isn’t going to be enough to clean them out. 

Chemical DE filter cleaners are available online or in pool supply stores and are usually diluted with muriatic acid and water, or just water, depending on the product and the noted instructions. 

Get professional help

When a grid is broken, a stain won’t come off, or your filter’s efficiency inexplicably drops, it may be time to call in a pool professional to do an inspection.

DE filter management is usually painless, but there are a few issues that take time to troubleshoot, from loose assemblies to missing or damaged O-rings, cracks in the assembly, and more. 

Consider bringing in a pool professional at least once a year to maintain your filter, and keep it running as well as possible, for as long as possible.

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