How to Clean and Refill a Pool D.E. Filter—The Right Way
Bought—or inherited—a fancy diatomaceous earth (D.E.) filter, but not sure what to do with it? Of all pool pump types, this is the most intimidating. After all, it’s the most expensive pool filter type, as well as the most maintenance-intensive. And it contains crushed, fossilized remains. Weird, right?
It’s time to demystify the D.E. filter, as well as the maintenance it requires to do its job well. We’ll go over what a D.E. filter is, its pros and cons, the options you have for cleaning your filter, the gear you’ll need to have on hand to get it done, and how to refill its filter media.
Is a D.E. filter really working for you? Now’s the time to find out.
What Is a D.E. Filter?
Inside D.E. filter tanks, you’ll find grids (also called fingers) which are covered in what appear to be white powder. Really, that powder is made from crushed fossilized remains of tiny aquatic organisms called “diatoms.” That’s right—D.E. filters are totally not kosher. But it gets even stranger: those diatom organisms have outer cell walls (or frustules) that are made out of silica. Sort of like the white little pouches that you’ll find at the bottom of packaging, or in pest control, cosmetics, and hygienic products.
D.E. made for pool filters is heat-treated to work as a filtration media, and it’s usually considered to be pretty good at that. D.E. filtration is often referred to as having the highest filtration capacity of all pool filters. And while it’s true that the D.E. filter can filter down to just 5 microns, if you change the sand media in a sand filter to filter glass, it’ll be just as efficient. If that comes as a happy shock to you, feel free to close this page and get a simple sand filter instead. I give my full permission.
D.E. Filter Pros and Cons
The only real D.E. benefit is how small it filters down—but again, a sand filter with the right media can do that, too.
The cons for a D.E. filter are a little longer. Perhaps the most worrisome one is that D.E. is a known carcinogen, and can give you a lung disease called silicosis (that’s from the silica!). That’s why when handling D.E. media, it’s super important to wear an N95 mask to prevent its particles from making their way into your lungs.
This filter is also the most expensive, highest maintenance filter on the market. And one headache involved with its maintenance is the fact that backwashing a D.E. filter could be illegal, depending on where you live. And no matter where you’re located, backwashing D.E. is harmful to the environment.
Since you probably already have a D.E. filter, I’ll still go into how to care for it. But I think it’s always important to know exactly what you’re dealing with, in case you want to make the shift to another pool filter type before learning some new, D.E.-specific skills.
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What Makes Cleaning a D.E. Filter Different from Other Filter Types?
So how is cleaning a D.E. filter different from other filter types? Well, it needs to be cleaned on a different schedule than other filter types—the recommendation is around once a month. For context, a cartridge filter should be lightly cleaned once a month but only deep cleaned one to three times a year. And a sand filter can’t be cleaned at all, only backwashed, which should happen when the filter’s pressure gauge displays 10 psi over its starting pressure.
Another difference for cleaning a D.E. filter is the amount of caution one should use during the process. When cleaning a D.E. filter, it’s essential to not only wear a N95 mask, but gloves and long-sleeved clothing. If D.E. comes in contact with your skin, you’ll need to rinse the area with water for at least fifteen minutes. If it comes in contact with your eyes, you’ll need to rinse your eyes for at least fifteen minutes, and remove your contact lenses (if you have them) after five minutes. While it’s essential that you don’t mix D.E. with any other chemicals or inhale its dust, you’ll need to call a doctor or a posion center if irritation of the lungs, mouth, eyes, or skin persists.
The Cleaning Process for a D.E. Filter
A D.E. filter is also unique because it has the ability to be cleaned in two different ways: a chemical wash (like a cartridge filter) and a backwash (like a sand filter). But this doesn’t exactly guarantee flexibility. In fact, you’ll need to wash your filter in both ways.
It’s recommended that you backwash the filter every six months or so depending on debris levels, or more specifically when your filter pressure gauge measures 10 psi above its normal operating pressure. That backwash should last 3–5 minutes, and end when the water runs clear from the backwash line.
Another part of cleaning your D.E. filter is disassembling the filter and cleaning once a month during the swim season to remove any caked D.E. powder. And it’s recommended that you replace your D.E. grids every 4–6 years depending on use.
What You’ll Need to Clean a D.E. Filter
Get this gear on hand, and you’ll be ready to clean your D.E. filter however it needs, whenever it needs:
- A backwash hose
- A garden hose
- O-ring lubricant
- D.E. filter cleaner
- D.E. powder
- A 5-gallon bucket
- Muriatic acid
- Safety goggles
- Acid-resistant gloves
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Cleaning Using D.E. Filter Cleaner
For a normal clean, this is the route you want to use. It’s quick, it’s easy, and it’s the least dangerous way to clean your D.E. filter. Do this regularly, and you might be able to avoid pulling out the muriatic acid.
- First, backwash the filter until the water runs clear. That’s probably about 3–5 minutes.
- Next, turn the pump off and open the air relief valve of your filter.
- Remove the drain plug and let water drain out of the filter tank.
- Also remove all clamps or latches that hold the filter together. The owner’s manual is particularly helpful for this step.
- Next, open the filter tank. Remove the filter manifold and take out all grids.
- Rinse out the filter tank with a garden hose.
- Clean the manifold: Use a nozzle on your garden hose to spray it down, making sure to flush all debris off the grids. If it’s looking pretty dirty, use a D.E. filter cleaner, following the manufacturer’s instructions. (If it’s really, really dirty, see the next section about using muriatic acid!)
- Use a garden hose to rinse the filter grids again, and flush out all debris and D.E. powder.
- Replace the grids in the filter tank.
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Cleaning a D.E. Filter Using Muriatic Acid
Was the manifold looking nasty, or you already know that regular filter cleaner isn’t going to cut it? It’s time to pull out the muriatic acid, but this should be done fairly infrequently. I recommend no more often than once a year.
And once a year is probably as often as you’ll want to do this, anyway. Working with muriatic acid can be a hassle because it’s a highly dangerous substance. It’s highly caustic and can cause injury to your eyes, skin, and lungs. Take all precautions when handling this chemical, and follow the manufacturer’s safety instructions to a T.
Here’s how to clean a D.E. filter using muriatic acid:
- Backwash the filter for 3–5 minutes until the water runs clear.
- Power the pump off.
- Open the filter’s air relief valve and remove the drain plug, so that water drains out of the filter tank.
- Remove all clamps or latches that hold the filter together. If you’re unsure how to open it, check the owner’s manual.
- Open the filter tank, remove the filter manifold, and take out all grids.
- Rinse the tank with a garden hose.
- Clean the manifold using a spray nozzle on a garden hose. Spray down the manifold to thoroughly flush all debris off the grids.
- Put on safety goggles, acid-resistant gloves, long sleeves, pants, and closed shoes. Dilute the muriatic acid with water in a 5-gallon bucket while following the manufacturer’s instructions for dilution. Place the manifold in the bucket, and make sure it’s completely covered with the diluted solution. Allow it to soak overnight.
- Use a garden hose to rinse the filter grids and flush out all debris, including the D.E. powder. Replace the grids back into the filter tank.
- Run the pool pump for at least 30 minutes to allow the D.E. to distribute evenly over the filter grids.
How to Backwash a D.E. Filter
This process is super straightforward—and if you’ve had a sand filter before, you’re no stranger to it. While you walk through this backwash process, just make sure the filter is never on while you’re turning that multiport valve:
- First, turn off the filter system. You don’t want anything running yet.
- Then, connect the backwash hose to the filter’s waste port. This will be where the backwash really happens in a second.
- Turn the multiport valve to “Backwash.”
- Turn the filter system back on, and let it go for about two minutes. Can you believe it? You’re already backwashing.
- Turn the filter system back off, and turn the multiport valve to “Rinse.”
- Turn the system back on and let it run for a minute or so.
- Again, turn the filter system off.
- Restore the multiport valve back to “Filter.”
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How to Refill a D.E. Filter
Ready to refill that D.E. powder? Remember, this is a dangerous substance, so proceed with caution. Here’s how to do it:
- Measure out how much D.E. powder to add by referring to your filter owner’s manual.
- Prime the pool pump.
- Remove the strainer basket lid and fill the basket with water. Allow some water to run through the incoming line.
- Lubricate the O-ring inside the tank with O-ring lubricant (shocker!).
- Replace the filter lid and tighten the clamps, bolts, or other fasteners to secure it.
- Open the air relief valve to release air from the filter tank.
- Turn on the pool pump.
- Close the air relief valve when water starts to come out.
- Mix the measured-out D.E. powder with enough water to make a thin, creamy solution. Be careful! And the pump should still be running—double-check that it is.
- Pour the mixture directly into the pool skimmer and run the pump for at least 30 minutes to distribute the D.E. evenly over the filter grids.
And that’s how you level up as a pool owner from “Intermediate” to “Advanced”! A D.E. filter is usually pretty intimating, but now you know exactly how to care for yours. You can even shock your friends by explaining what’s actually in that D.E. filter tank—the pool care equivalent to pulling out a pet iguana. Enjoy!