What is a Diatomaceous Earth (DE) Pool Filter?

If you have a pool that you just can’t seem to keep clean, then installing a DE filter may just be the way to go.

What is a Diatomaceous Earth (DE) Pool Filter?

A DE pool filter uses Diatomaceous Earth as a filter medium. Essentially, there are screens (grids) inside the filter housing which are covered in DE power, pool water is then forced through the filter and the impurities are trapped in the DE and grids.

Out of all the pool filters, DE filters are best for filtering pool water in terms of filtering capacity and efficiency. They will give you the clearest water.

Diatomaceous Earth (DE) Pool Filter

How Much Do DE Filters Cost?

Diatomaceous earth filters cost between $520 and $2,000 to purchase. The exact cost depends on the size of the size and brand of the filter.

In addition to a larger upfront cost, a DE filter is also more expensive to maintain. Like sand filters, DE filters need regular backwashing. And each time the filter is backwashed, you’ll need to recharge the DE. The cost is between $5 and $15 to do this.

Additionally, you may need to occasionally replace the filter grids at a cost of $15 to $40 per grid.

ComponentCost
DE Filter Purchase Cost$520 to $2000
DE Filter Powder Media$20 to $40 for a 24 lb bag
DE Filter Grids$15 to $40 per grid

What is Diatomaceous Earth?

Diatomaceous earth (DE) is made up of microscopic, sponge-like prehistoric organisms.

They possess the power to absorb huge quantities of water impurities. The use of diatomaceous earth in water treatment and filtering systems results in crystal clear water that requires much less treatment with chlorine and other chemicals.

Diatomaceous earth was first discovered in the late 1830s in Germany and deposits are found all over the world.

It is used in a variety of industries, primarily filtration, pest control, agriculture, and heavy industry.

DE Filter Maintenance

Overall, DE filters do require less maintenance than other types of pools filters.

  • Backwashing (once every 1-3 months)
  • Inspection, clean, and/or replacement of grids (yearly)

Backwashing

You’ll need to backwash a DE pool filter once every few months rather than every two-four weeks required with a sand filter.

Backwashing causes the loss of a large volume of pool water and chemicals which need replacement. This adds to the cost of pool ownership, not to mention it is unfriendly to the environment. DE pool filters are a greener option as they require fewer backwashes resulting in less water and chemical usage.

Here’s a full guide on backwashing a DE filter: How to Backwash a Pool Filter & How Often

The higher efficiency of DE pool filters also means that less chlorine is needed to maintain water quality.

While the initial installation costs are higher for a DE pool filter, some of this cost is recouped in lower running costs.

Hayward EC40AC Perflex Extended-Cycle D.E. Pool Filter

Top Up of DE

Unlike a sand filter, after backwashing a DE pool filter, you’ll need to add a quantity of diatomaceous earth to replace the powder lost during the backwash and cleaning process.

But this is more than compensated for by the reduced use of chemicals.

Here’s how to do it: How to Recharge or Refill DE in Pool Filter

Yearly Inspection and Clean

With a DE filter, on a yearly basis, you’ll need to open it up and give it a good clean. This involves removing the grids and cleaning them.

If you notice any tears or rips, you’ll need to replace the grids. If you do need to replace them, they’ll cost $15 to $40 per grid.

Pros and Cons of DE Filters

Pros

  • Extremely efficient at removing debris from the pool.
  • Backwashing is only required every 4-5 weeks compared to fortnightly with sand pool filters.
  • Less chlorine is required to keep the water free of bacteria and viruses.
  • Less time is required to maintain the pool.
  • Saves on the water as less backwashing is required.

A big plus is that your pool requires fewer chemicals to keep it clean due to DE’s filtering efficiency.

Any microscopic debris in the pool is caught in the DE filter grids, leaving the water sparklingly clean. Diatomaceous earth (DE) filters can prevent particles of 3-5 microns (µ) from circulating in your pool. A micron is 39 millionth of an inch (0.000039), so a DE pool filter can remove large bacteria (1-3µ).

For comparison, a grain of pollen is only 15µ and invisible to the naked eye.

You will also spend a lot less time maintaining your pool. The DE filter catches a much higher quantity of contaminants in the pool water. This means you’ll need to spend less time adding chemicals.

And finally, out of all the pool filters, DE filters require the least amount of maintenance. Both sand and cartridge filters require more cleaning. Sand filters require backwashing, which is straightforward but must be done about every 4 weeks.

Cartridges filters take a few hours to clean when they do need cleaning. They need to be disassembled, hosed out, and possibly soaked a few times a year.

Cons

  • Initial costs are higher than both sand and cartridge pool filters.
  • The filter grids must be cleaned after each backwash.
  • Diatomaceous earth adds to the cost of maintaining the pool.
  • Clog up quickly

The biggest downside of DE pool filters is the cost. They cost more to purchase and install and the ongoing costs are the highest out of the three different types of pool filters.

Another downside is that DE filters do blog up quickly, especially with algae. This is both a pro and a con. It’s great that the filter captures the smallest things but at the same time, they are more susceptible to blocking up quickly.

If you however maintain your pool well, by keeping the water balanced and regularly vacuuming and scrubbing the walls, you’ll avoid this.

DE Pool Filter Comparison Chart

To make comparisons easier, here’s a chart of the 3 most popular types of pool filters.

FilterMaintenanceOngoing CostsCostFilter Efficiency in Microns
DE FilterDE Filter Grid and DE PowderBackwash Bi-Monthly

Add DE After Backwash
$520 – $2,0003 – 5
Sand FilterSandBackwash Bi-Weekly

Replace Sand – 5 five years
$300 – $1,20020 – 100
Cartridge FilterFilter cartridgesReplace Filter 2 – 5 years$200 – $1,60025 – 100

How Do DE Pool Filters Compare to Sand and Cartridge Pool Filters?

Diatomaceous earth (DE) pool filters (DE) are similar to sand pool filters. Sand is used in one and DE powder is used in the other.

A pump forces water through the sand and or DE powder, trapping impurities.

A DE pool filter is also similar to a cartridge pool filter. A cartridge filter uses material filter cartridges while a DE filter uses filter grids that become coated with diatomaceous earth to filter the water.

These cartridges are available as both reusable and disposable items, whereas the DE grids are washed and re-used after backwashing. The DE powder also needs refreshing after backwashing. It cannot be reused.

To give you an idea of the 3 filters’ relative efficiency, here is the size of particles each one can remove from your pool water:

  • Diatomaceous earth: 3-5µ
  • Sand: 20-100µ
  • Cartridge: 25-100µ

The DE pool filter is the clear winner (pun intended!).

How Much Diatomaceous Earth Do I Put in My Pool Filter?

DE filters have a recommended amount of DE powder that you must add to a fresh filter.

If your filter doesn’t have a manufacturer’s reference, then you can use a pound of DE powder per 10 square feet of filter, as a rough guide. That is only on the initial dose.

Subsequent backwashes will vary, as the amount of powder that you add depends on your particular pool’s requirements. Usually, for top-ups, you’ll need about 80% of the full capacity of powder.

How to Add DE Powder to Your Pool

It takes around 4-6 pounds of DE Powder to coat the grids.

Bags of DE powder are available in 25-pound increments and last about 4-6 separate backwashes. You can expect to pay in the region of $20-40 for a 25-pound bag.

EasyGo Product Celatom Diatomaceous Earth DE Pool Filter Aid – Swimming Pool & Spa Filtration – - 25 Pounds

Here’s how you determine the required amount of DE Powder for your pool:

  • Initially, you should use the full recommended amount as stipulated in your filter manual. But if you are replacing DE Powder after a backwash, then you don’t have to add the full amount, generally only about 80%.
  • The grids retain some DE Powder and adding too much DE powder will result in any excess being deposited into your pool as the filter runs.
  • The best way to establish how much DE powder to add is to monitor the pressure gauge. Stop adding DE powder once the pressure reaches your normal range which is around 10-13 psi.
  • You’ll see some cloudiness as the water enters your pool if there’s too much DE in the filter. Add a pound less the next time you backwash. Keep reducing the quantity until you don’t see any cloudiness entering the pool after backwashing is complete.

The Process:

To add Diatomaceous earth powder to your pool filter:

  1. Switch off the power and check that the multiport valve is set to the filter mode.
  2. Open the air relief valve to let the air out of the filter.
  3. Turn the pump back on and let it reach the prime.
  4. Close the valve once a steady stream of water flows out of the valve.
  5. Mix a thin slurry of DE powder and pool water then add the mix to the skimmer.
  6. As the water creates a “cyclone” in the skimmer, add your DE powder (be careful not to breathe any of the powder into your lungs!).
  7. Don’t dump all the powder in at once else the pipes may clog. Rather add it at a slow and steady rate.
  8. For safety, check the pressure gauge and when it reaches its normal operating pressure, stop adding powder.

Safety Considerations When Using Diatomaceous Earth

You may be wondering if using diatomaceous earth in your pool is safe?

Manufacturers treat pool grade or filter grade diatomaceous earth with high heat. This calcination process transforms the silicon dioxide into crystalline silica, which is carcinogenic.

You should be very careful when filling your pool skimmer as pool grade DE is toxic. Consider wearing a mask as the powder is easily inhaled into your lungs.

It should only ever be used for filtration.

Frequently Asked Questions (FAQ’s)

Here’s some common questions concerning DE pool filters.

How Much Do DE Pool Filters Cost?

You can expect to pay between $520 and $2,000 for a diatomaceous earth pool filter. The final cost will depend on its size and complexity. It is the most efficient pool filter and provides the best results.

Do You Use Chlorine with a DE Filter?

All filters only remove particles or debris from the water. While DE pool filters can remove larger bacteria, there are other bacteria, viruses, and organisms that chlorine will kill.

Almost all pools use a chemical such as chlorine to purify the water. The filter then removes excess impurities. For optimum results, pH levels must be monitored and maintained when chlorine is added.

What is DE Filter Grids Made Of?

DE grids are constructed using plastic and woven polyester material.  Backwashing DE filter cleans off the diatomaceous earth layer that covers the surface of the grids. Once backwashing is complete, the grids can be hosed down and left to soak for a few hours to remove most of the DE from the material.

Where to Buy Diatomaceous Earth?

You can buy DE in a variety of quantities in 25-pound increments. Retailers, hardware stores, and pool supply stores stock DE.

Just be certain that you are buying the correct grade of DE. Food grade DE is not suitable for pool filtration systems.

How Do I Remove DE Powder from My Pool?

DE powder sinks to the bottom of your pool where it is easily vacuumed up.

When vacuuming the DE out of your pool, keep the pressure release valve open so that the DE-contaminated water will flush out of the system.

Remember that DE is both toxic and can clog drains and pipes. For this reason, many cities do not allow DE to be flushed into the sewer or stormwater drains. A separation tank is usually fitted into which the wastewater is pumped.

A strainer is fitted that catches the DE which you can then dispose of in the trash.

How Many Grids are in a DE Filter?

DE pool filtration systems usually have eight equally sized grids.

How Long Do DE Pool Filters Last?

A DE pool filter can last between five and ten years.

Which Type of Filter System Will Remove the Smallest Particles?

DE pool filters can remove particles from the water that are between 3 and 5 microns.

To ensure that they operate optimally, DE pool filters are backwashed every 2-3 months. This is required when the pressure exceeds normal operating levels by 10 psi. After backwashing, additional DE powder is added to the filter to replace that which was lost during the cleaning process.

Can You Swim After Adding DE to the Pool?

It shouldn’t take very long for your DE pool filter to work once you restart it after a backwash. You should wait at least an hour after adding any balancing chemicals to your pool.  If you add chlorine, then wait between two and four hours before swimming.

Why Does My DE Pool Filter Keep Clogging?

DE Filter grids can become clogged with oil. Avoid swimming when using oily sunscreens and rather wait for them to be absorbed into your skin. Algae also block up DE filters.

Do You Have To Add DE Every Time You Backwash?

Yes, after backwashing, you must add DE to the filter. Always use the recommended quantity of DE for your filter. If DE enters the pool, wait for it to settle and vacuum it out of the pool via the waste port.

In the future, use one pound less DE, reducing it each time until no DE is entering the pool after the backwashing, cleaning, and topping up process is completed.

When Should I Replace My DE Filter Grid?

DE filter grids can last for many years before they require replacement. Check that the material is intact when you wash the grids. You may have to replace them after 2 or 3 years if the pool has been heavily used.

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