Pool DE Filters 101: How They Work, Pros & Cons, Best Options, & Your Questions Answered

Written by Michael Dean
December 14, 2023

pool DE filter

DE filters can be used on both above ground and inground swimming pools, and they are relatively easy for a homeowner to work with, making them a popular choice for many pool owners. But if you don’t know anything about this type of filter, it can be overwhelming to understand how it works, let alone how to look after it! Whether you are new to swimming pools in general or you’re thinking about switching to a DE filter, this guide is for you.

Here, I will cover the basics of a DE filter, including what they are, how they work, pros and cons, comparisons to other filter types, cleaning tips, and more!


Main Takeaways

  • DE filters use Diatomaceous Earth, a specific ground-up fossil, to filter the water.
  • DE filters are relatively inexpensive and is great at filtering out smaller debris, but it can require more maintenance than other filter types.
  • To clean your DE filter, make sure you backwash regularly. At times, you may also need to remove the grids completely from the filter to rinse them out.
  • DE grids can last many years, but they will eventually wear out. You’ll need to replace them every 5 to 10 years.

What Are DE Filters, And How Do They Work?

Pool DE filters use an extremely fine substance called diatomaceous earth (DE) to coat the grids within the tank and filter the water. DE is a natural, fine powder composed of fossilized skeletons of tiny organisms called diatoms. DE particles are very porous because of the hollow nature of those organic structures. They are well-suited for filtering water and can capture teeny tiny debris. 

They function quite differently than other filter types, as you must replace the DE powder each time you clean out the filter.

Diagram: A) Upper manifold, B) Standpipe, C) Bulkheads, D) Pressure gauge, E) Air relief valve, F) Air relief tube, G) Filter grids

When you add DE to your filter, the substance binds to the filter grids inside the main tank. These grids are held in place by a top and bottom manifold, pressure plates, and a gasket. The filter grids can come in a few different forms: curved plates, cartridges, or several tube-like “fingers.” More on this below.

Once the grids are properly coated with DE, they will be ready to start cleaning the water. Your pool pump will force dirty pool water through the DE-coated grids, trapping debris. The clean water exits the filter tank via a valve and returns to your pool. It is almost magic how quickly a DE filter can turn a cloudy pool into a sparkling paradise!

Some DE filters have a bump handle. This mechanism shakes and agitates the DE around on the grids and exposes a fresher layer of DE. This device will prolong the amount of time between backwashes and cleanings.

Adding DE Powder

If you have a DE filter, you will get very used to cleaning and adding new DE powder. Adding DE is done by pouring some into the skimmer’s mouth; the amount varies by model, but a typical ratio is approximately one pound of DE to every five square feet of filter grids. Doing so is a bit of a messy job, so prepare the area and wear proper PPE. Inhaling DE can be harmful to your lungs, so I highly recommend wearing gloves, goggles, and a mask.

Once the DE is mixed with water in the skimmer, it is sucked into the filter tank, where it gets trapped on the fingers of the grids and starts filtering your water.

Different Types of DE Filters

All DE filters have at least one thing in common: they use diatomaceous earth to filter the pool water. That said, the design of these filters can be slightly different. Here is a quick breakdown of the three main DE filter designs.

DE Filter with Grids

The most common type of DE filter is one with curved grids. The grids are made of a fine mesh material that connects with a manifold inside the main tank. These grids block DE but allow water particles to pass through them. Most filter grids are curved, but some are straight.

DE Filter with Fingers

The other type of DE filter design is “fingers.” The filter system on a DE filter with fingers looks completely different than one with grids and a manifold. In this system, there is a collection of finger-like tubes that the water must pass through to get back to the pool. This system is much more complicated to clean and maintain as you must take the entire system apart to clean it.

DE Filter with Cartridges

The final type of DE filter is a quad or cartridge DE filter. These are the least common but are effective at cleaning your pool water. Quad DE filters have four cartridges that collect with DE. The cartridges allow water to pass through but block the DE particles.

Pros and Cons of DE Pool Filters

DE filters are one of the most common types of pool filters on the market. While most residential pool owners opt for sand and cartridge filters for their ease of use, DE filters are the most effective filtration systems. Let’s dive into some of the positives and downsides of owning a DE pool filter.

Pros

  • Most effective filtration system. Can filter debris as small as 3 to 5 microns!
  • Due to the larger filter area, you won’t need to backwash as often as a sand filter.
  • Will make your pool water cleaner and safer than other filter types.

Cons

  • DE can make a bit of a mess.
  • DE filters are more expensive than sand and cartridge filters.
  • DE needs to be changed frequently, especially when the water is very dirty.

Let’s see how those benefits and drawbacks compare to other popular swimming pool filters.

DE Filters vs. Sand Filters

While DE filters use tiny particles of diatomaceous earth to filter pool water, sand filters use specialized sand. DE and sand filters are similar in that they need to be backwashed periodically. But sand pool filters can typically run a bit longer before they need a backwash to clean them. They both are equipped with a valve to adjust the water flow and make backwashing possible.

The DE Must Be Replaced After Backwashing

Unlike a DE filter, you do not lose sand from your sand filter when you backwash. It all remains in the tank. On the other hand, when backwashing a DE filter, you rinse away all of the DE and the dirt caught in it. That means you must add a new DE to a DE filter system each time you backwash.

DE Can Be Hazardous

Since some people are very sensitive to exposure to DE, it can be a bit of a hassle to work with when adding it to the system. It’s also not a good idea to inhale DE if you can avoid doing so, as the dust can be dangerous for your lungs.

You can always wear a particulate mask to minimize health risks, but that does add another step to the job, and you’ll be working with DE often.

DE Filters Much Smaller Particles

While sand filters do a decent job of filtering out small particles in the water DE is much more effective. In fact, DE filters can filter particles as small as a red blood cell!

DE Filters Are Messier and Require More Maintenance 

DE also tends to make a bit of a mess. If you add it to the skimmer’s mouth too quickly and overwhelm the suction, some of the DE will float back out of the skimmer and fall to the bottom of your pool, and you’ll need to vacuum it out.

And, even if you are pretty careful, you’ll probably end up spilling some on your deck while adding it and schlepping it back and forth from wherever you store it. It’s easy to clean up with a hose and doesn’t stain. But it is an eyesore, and if you accidentally rinse it into your pool, you might have to get your vacuum out.

One strategy to minimize spilling is to buy small, single-use bags of DE. Instead of buying a big bag or box of DE intended to last a long time, the smaller bags are usually sized to meet the need for one application of DE after a backwash. But they are much more expensive.

DE filters also have a grid system, and sand filters do not. So, in addition to the expense of DE itself, you may have to replace the grids periodically if they develop a rip or begin to deteriorate.

DE Filters vs. Cartridge Filters

DE filters and cartridge filters are alike in their design. A system of grids sits inside the tank and filters the pool water as it is forced through the tank by the pump. That said, cartridge filters are MUCH easier to maintain.

Cartridge Filters Don’t Require Backwashing

Cartridge filter grids are designed to be cleaned periodically, but you won’t have to backwash them. You will simply remove the cartridge, rinse it off, clean it, and place it back in the filter. DE filters must be backwashed, cleaned, and refilled with DE frequently.

A DE filter can’t keep your water clear and clean after it gets clogged with debris, and the tank pressure will build quickly. You should expect that a DE system will require a lot of backwashing when the pool is quite dirty, like when you first open it each season or after a heavy storm.

Sometimes, that will mean multiple backwashes every day until the water clears up. And you will likely have to backwash after each vacuuming.

If you’re considering a cartridge filter, read my guide on replacing your pool filter cartridge.

DE Filters Finer Particles Than Cartridge Filters

DE filters down to a much finer level of debris than either sand or cartridge filters. While this makes your water cleaner, the filter will get clogged faster and need more frequent cleaning.

In comparison, a cartridge filter can run for a much longer time without cleaning.

DE Filters Are Better for Larger Pools

Cartridge filters are definitely the easier option, but if you have a large pool, you’ll likely need a DE or a sand filter. Cartridge filters are perfect for small pools and hot tubs.

DE Filters Are More Expensive

Lastly, DE filters are typically much more expensive than cartridge filters. They also have more complex parts and are more costly to repair.

Check out my sand vs. DE vs. cartridge filter guide for a much more in-depth comparison.

Criteria You Should Consider When Looking for DE Filters

DE filters need to be sized appropriately to handle the volume of water in your pool. Look to your filter manufacturer to determine which size is best for your application.

It’s fair to say that DE systems operate in a bit of a sweet spot. If the pool is of moderate size, DE is perfect. If it is very small, a cartridge system will likely be your best bet, as it can handle all the water filtering for long stretches of time without needing to be cleaned.

A very large pool with a tremendous volume of water is probably too much for a DE system to handle, as it will need to be backwashed very often.

DE is a common choice for homeowners taking care of their own pool because it is a very efficient system that is relatively easy to work on when needed. Just make sure that the manufacturer’s specifications are in line with the size of your pool.

Best DE Filter Brands

Brands like Hayward, Pentair, and others are known for making some of the best DE filters on the market, and I tend to agree. For more specifics, check out my guide on the best pool filter.

Tips for Cleaning Your DE Filter

Cleaning your DE filter can be a pretty long and frustrating process. While you generally only need to backwash and add more DE, occasionally, you will have to disassemble the filter and clean the grids individually. Here are some tips for making the process of cleaning your DE filter easier.

Backwash Properly

When backwashing, shut the pump off and turn the valve to backwash mode. Never adjust the valves while the pump is on, or you can ruin the gasket within it.

Once you’re in backwash mode, turn the pump back on and wait for the water to run clear. If you can’t see it exiting the plumbing because the waste valve is buried, there is usually a sight glass on the valve itself. Once the water is clear, shut the pump off.

Next, turn the valve to filter again and run the pump for a few seconds. This will agitate the fingers and shake up the remaining DE. Repeat the process and backwash once or twice to eliminate as much of the spent DE as possible.

Check Your Grids and Deep Clean Them Occasionally

Periodically, washing the grids of your DE filter may be necessary. It is a good practice to do so once or twice a year, especially at the end of the season. Doing so will keep the DE from growing any algae or mold.

To rinse the grids, open the tank’s clamping system and set it aside. Remove the top manifold, and open the bottom drain plug on the filter tank. You can rinse the grids in place with a hose. Or, if you want, remove them from the tank and rinse them somewhere else.

Know When It Is Time to Replace the Grids

If your filter grids are becoming increasingly more difficult to clean and have a permanent layer of gunk or build-up, it may be time to replace them. DE filter grids can last up to a decade if maintained well. 

How to Add DE Powder to Your DE Filter and How Much to Add

After a thorough backwash, go to your DE stash and bring some to the skimmer. Do not delay adding DE after a backwash, or the grids could become caked with debris and reduce the efficiency of the system.

Open the top lid of the skimmer, and add the manufacturer’s recommended amount of DE. Typically, that will be about one pound of powder for every five square feet of grid surface. A scooper like an old coffee can come in very handy. You can read my guide on how much DE to add to your filter for more specific measurements.

Ensure that you add the DE slowly so as not to overwhelm the skimmer. This will help avoid having any DE fall back into the pool itself. When you’re done, put away your DE and rinse any that spilled off the deck, being careful not to get any in the water.

How Long Do DE Filters Last? And When Is It Time to Replace Them?

DE grids can last many years. The fabric of the grids tends to become brittle and deteriorate after ten or so seasons. However, some users may get more life out of a set while others might not. It’s sort of the luck of the draw and determined by how dirty your pool gets and how well you maintain the balance and chemistry of the water.

You’ll know it’s time to replace the grids if the water seems to remain cloudy even when running the filter for a long time and backwashing routinely. Another sign that you need to replace the DE filter grids is the appearance of DE in the pool.

If there is a bit of DE shooting out of the return jets, it is a pretty good indicator that there is either a rip in the grids themselves or a crack in the manifold.

At that point, it is time to inspect the internals of the filter system and replace anything that is no longer working right. Since DE filters are very common, buying a whole new set of grids is pretty easy, and they aren’t too expensive or difficult to change. For more on replacing them, head to my guide on DE filter grids replacement. If you don’t think it’s time to replace them quite yet, you can read my guide on diatomaceous earth pool filter problems to troubleshoot what might be happening.

If you don’t want to open up the tank, it’s probably time to call in a pro.

Diatomaceous Earth: The Ferrari of Pool Filters

DE filters are the most effective option for pool filtration on the market. So, if you are looking for something that will clear out the smallest of particles, this is the option for you! Would I recommend a casual pool owner to use a DE filter? Probably not. These filters require a lot of maintenance and are a bit complex to clean and set up for the average pool owner. But DE is your best bet if you have a large pool or are managing a commercial pool!

Alright, that’s about it for DE filters. Have any questions? Drop me a line; I’m always happy to help!

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