My D.E. Filter Keeps Clogging Up

My D.E. Filter Keeps Clogging Up

Filtering down to a ridiculously small 2-3 microns, a diatomaceous earth (D.E.) filter far outperforms sand and cartridge filters. The result is clearer, cleaner water with fewer corrective chemicals needed, since the water has fewer suspended solids.

But being the best type of pool filter is not the only thing they say about D.E. pool filters, they are also known to require more maintenance. You have to add the D.E. powder after backwashing, and at least once per year you have to open up the tank after backwashing, and spray the grids clean – a messy and wet job.

And, because of the small pores and relatively small filter surface area, as compared to pleated cartridge filters, D.E. filter grids can get gummed-up. The thick polyester fabric is stretched over the frame and sewn tightly.

Now, here’s an important distinction. The filter grid is not the filter – the powder is the filter. Grids are just the surface that the D.E. cake builds upon. After passing through the D.E. layer, the water passes through the filter grid fabric, before being pushed into the manifold and out of the filter tank.

1. D.E. Filter Grids Clogged with Oil

Small amounts of oil inevitably find their way into your open air pool. Much is brought in on the wind, or dragged in by swimmers. Pool lubricants and some gel type pool clarifiers can add oils to your pool, which eventually is trapped in the filter grids.

Using a degreaser like TSP, or our D.E. filter cleaner product, soaking to remove oils is a good treatment every year or two, to remove D.E. grid fabric clogging oils. For severe oil problems, use a pool enzyme, and use Perlite D.E. powder substitute, which has twice the oil absorption capacity as D.E. powder.

2. D.E. Filter Grids Clogged with Scale

D.E. filter cleaner

Another type of pore-clogging material is the opposite of oily, it’s scaly – minerals like calcium and magnesium, common in hard water areas, can come out of solution in certain situations, and clog a D.E. filter grid, so that hosing does not remove the scale.

Using a 10% acid solution, pour a gallon of muriatic acid into 10 gallons of clean water, in a very clean trash can. Soak the grids or grid assembly for a few hours to remove mineral scale deposits from D.E. grids. TSP or other degreasers won’t remove scale, and acids won’t remove oils – but our multi-purpose D.E. Pool Filter Cleaner chemical removes both oil and scale deposits.

3. D.E. Filter Grids Clogged with Baquacil

A third type of problem occurs in D.E. pool filters that are used on pools treated with Baquacil, or other Biguanide pool sanitizers. Such a well known problem in fact, that manufacturers of biguanides for pools recommend a sand filter, and recommend changing the filter sand every 1-2 seasons, or when filter cycles shorten.

4. D.E. Filter Grids Clogged with Gel Clarifiers

Certain types of pool clarifiers, such as Sparkle Plus, or MiraClear – are not compatible with D.E. filters, as they tend to gum-up the filter grid fabric, or don’t backwash completely. Natural Chemistry Filter Perfect would be a good solution to removing it, after removing to hose the grids and tank clean.

5. D.E. Filter Grids Clogged with Algae

For those of you who have dealt with many algae blooms, residue from previous algae blooms can still be harboring deep inside of your filter grids. After treating a pool for algae, I like to remove the grids to hose the grids and tank completely clean.

For severe pool algae blooms, soak the entire D.E. grid assembly (after hosing clean) in a 10% bleach solution for several long minutes, before rinsing thoroughly (or soaking in the pool).

QUESTION 1: 

When people tell me that their D.E. filter is clogging up in hours or a matter of days, my first question is about the size of the filter, to make sure it’s large enough for the pool. Hayward Perflex D.E. filters, or small 24 SF D.E. filters installed on inground pools for instance, often need extra cleaning care.

QUESTION 2: 

My second question is always “are you using enough D.E. powder?” Of course they always say they are, but remember that 1 lb of D.E. powder is more than a 16 oz cup, it’s a 32 oz cup. I know that’s confusing but because of it’s fluffy nature, it’s measured by volume. And make sure to use pool D.E. powder (or Perlite Powder) – not your garden variety type of D.E. powder used to control insects!

QUESTION 3: 

Then I ask them if they have tried a D.E. filter cleaner yet? And I stress the D.E. part – because sand pool filter cleaners, or the granular stuff, are too harsh for filter grids and cartridges. Be sure to use only D.E. Pool Filter Cleaner, or the Natural Chemistry cleaner, Filter Perfect.

18 thoughts on “My D.E. Filter Keeps Clogging Up

  1. Hello. My breather tube at the top of my pentair FNS plus system clogs with DE about every 2-3 days causing the pump water level in the sight glass to drop and drop in flow pressure of the pump. What could be causing this to continually clog! Getting very frustrated having to pull the filter lid every week and remove the clog from the breather tube mesh filter

    • HI Bryan, that is normal for that to clog, and I don’t think it could possibly be related to the flow rate from the pump. You don’t need to clean off the mesh strainer. If your pump is losing prime, look for an air leak in front of the impeller, from a loose pump lid or loose pipe coming into the pump, those are the usual suspects.

      • Bryan janovick

        The strange thing is that once I remove the blockage on the breather the pump sight glass will fill back up. Also when clogged my heater will show error code for low flow. Once I unclog the breather the code usually clears on the heater. 🤷🏼‍♂️

        • Bryan, probably that’s because the DE powder is falling off of the grids, and mixing up with the dirt, which is restoring flow rate and reducing pressure. I’m sure you know that the function of the breather is to remove air that is in the filter tank, by drawing it into the tube and pushing it out into the pool. And the strainer is to keep the tube from clogging and also to keep DE from entering the pool. You can also open up the air bleeder under the pressure gauge, to release air in the tank. If there is a constant influx of air into the filter, then check for an air leak, before the impeller. But you could pull of the mesh strainer and plug up the air intake hose, and it should not affect the flow or pressure.

  2. My DE filter keeps losing prime I believe I definitely have enough DE in it cleaned it at the beginning of the season pool was green did liquid chlorine shock algicide and clarifier we cleaned out the filter and put fresh DE when I add the DE it seems like the prime instantly goes away within a couple hours

    • CHeryl, I assume that your filter pressure is high when the flow slows down? If so, it is a filter problem, If low, it may be a pump problem. If high psi, remove the screws and pull out the grids or fingers, and hose off well, then soak in TSP to degrease, rinse and then soak in a 10% acid solution to descale, rinse and replace with fresh DE.

  3. I have a quad 60 pentair filter that is 3 years old.this year I am fighting with high cyanuric acid issue’s. I’m in Texas it’s too hot to drain the pool down right now I’m told it could damage the surface. I have been fighting algea continuously have cleaned the grids 2 times zone may 1 the pool builds pressure too fast within 10 days I have to backwash constantly. Is there any way I can change this.?Thanks

    • Hi Butch, the DE powder you are using, if it is a new brand, it may be to blame, mis-labeled, or poorly mined and processed perhaps. For they cyanuric, you can drain the pool in this heat, unless the plaster is within 30 days old, it will cause no issues. Just do it quickly, within 1-2 days.

  4. Jim Messina

    We have a very old(more than 30 years) Hayward de filter for an inground pool. No separate holder for the powder. This year cannot get the water clear nor the heater to run. Man at the pool store said to backwash, clean everything and put in new de. However we did all that 2 days ago. He said he still thinks it’s clogged from all the pollen and he’d be happy to sell us new sand filter. Anyway, I’m wondering if we’re using too much powder. There’s no chart on the outside of the tank. How do I calculate the square footage of the filtration area. The tank is about 21” in diameter with those long fingers that hang down

    • Hi Jim, you have a Hayward Perflex DE filter, they use either 4, 5 or 6 lbs of DE, depending on what size model you have. It should say on the label, the amount of DE, or the filter model EC-50, EC-65 or EC-75. Remember that a lb of DE powder is not 16 oz dry measure, but 32 oz dry measure. The trick for these filters is to remove the filter assy, or “Nest Assy”, and hose them off real well, then soak them in a 5-gal bucket of very warm water with 1 lb of TSP, to degrease the fingers. Then hose off well. If you suspect mineral scale on the fingers, follow up with a soak in a 10% acid solution to dissolve any scale on the fabric. Rinse again and reinstall with a FULL charge of DE.

  5. Jeff Lilge

    Davy, I live in Michigan. At end of every season I soak my DE filter fingers in the recommended cleaning solution from pool store & then rinse. Just opened the pool last night and this morning the pressure was high and DE filter was very stiff. Was able to get it to bump and pressure came back down. This over night or every couple day scenario has been the case over the last year or so. Any ideas?

    • Soaking the finger assy in a TSP solution may help, it will remove grease and oils. Don’t use a polymer clarifier, altho you can use natural SeaKlear 4-in-1 clarifier. Be sure to add full 32 oz ‘pounds’ of DE to the filter (not 16 oz), because DE is so fluffy, one lb is actually 32 oz dry measure.

  6. My pool has been taken over by algae. I have chemically treated the pool and now need to run the filter to clean and vacuum out the remains. The only problem I am currently having is that every 10-15 minutes, the pressure jumps to 20 and no longer moves water and the vacuum no longer is working. When I pull out the grid, it is covered in green slime. Is this normal? We have been cleaning and adding DE powder every 15 minutes. Is there a different solution? Is this a sign of not using enough DE powder?

    • Emily, if you do not use the correct amount of DE powder, or if you use far too much powder, it can cause ‘short cycling’ or quick clogging. One tip is to know that 1 lb of DE powder is not 16 oz dry measure as one would assume, but actually 32 oz. dry measure, because DE is so ‘fluffy’. So if your filter calls for 4 lbs of DE, that would be 4 x 32 or 128 oz, or 1 gallon, but dry measure. Your filter grids may also be coated in grease or scale. Soaking the grids in a DE Filter Cleaner would be recommended. You can also use TSP to remove the grease, and a mild acid solution to remove scale. If your pool is still green, add more shock – keep adding until it turns blue/grey. And be sure the pH is good and low, around 7.2, where chlorine is most potent.

  7. I replaced my de grids 11 months ago so they are still white and structurely sound. I have high phosphate so I added 50 oz PhosFree. My pressure now climbs from 17psi to 25psi about 2 hrs after backwashing. I cleaned the grids, added 4 lbs de and it happened again. I think i am using too little de. Will a grid soak help? How much tsp should I use?

    • Hi Jim; I believe that is what happens when using PhosFree, as it removes the phosphates from the water. Should be temporary, but if it does continue, you can soak DE grids in TSP to remove greasy gunk, use 1 lb per 10 gals of warm water. Rinse well after soaking for 4-8 hours. If you believe that mineral scale is clogging the grids, soak in a 10% muriatic acid solution for several hours, and then rinse well.

  8. Julie Sevilla

    what is causing my DE filters to turn green? No algae in the pool, the filters are 6 months old. we backwash 1x a week, I have never seen them green before.

    • Hi Julie, might be a pollen of some sort? If you dont see algae in the pool, it may not be algae in the filter – green jello perhaps from a prankster?

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