Swimming Pool Blog
Rob Cox November 21, 2016
Diatomaceous Earth Pool Filter - Clogging Problems and Solutions
Now here's a blog post with some practical use. If you're the owner of a Diatomaceous Earth pool filter, aka DE filters, this post will help you keep it operating in tip-top condition.
The D.E. pool filter is the most superior type of pool filtration available. Filtering down to a ridiculously small 2-3 microns, a DE filter far out-performs 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 DE pool filters, they are also known to require more maintenance. You have to add the DE 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, DE filter grids can get gummed-up. A DE Grid is a fabric covered plastic frame. The thick polyester fabric is stretched over the frame and sewn tightly.
Now, here's an important distinction. The DE filter grid is Not the filter - the DE powder is the filter; DE grids are just the surface that the DE cake builds upon. After passing through the DE cake or layer, the water passes through the filter grid fabric, before being pushed into the manifold and out of the filter tank.
DE 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 DE filter cleaner product, soaking to remove oils is a good treatment every year or two, to remove DE grid fabric clogging oils. For severe oil problems use a pool enzyme, and use Aqua-Perl DE powder substitute, which has twice the oil absorption capacity as DE powder.
DE Filter Grids Clogged with Scale
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 DE filter grid, so that hosing does not remove the scale.
Using an10% 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 DE grids. TSP or other degreasers won't remove scale, and acids wont remove oils - but our multi-purpose DE Pool Filter Cleaner chemical removes both oil and scale deposits.
DE Filter Grids Clogged with Baquacil
A third type of problem occurs in DE 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.
DE Filter Grids Clogged with Gel Clarifiers
Certain types of pool clarifiers, such as Sparkle Plus, or MiraClear - are not compatible with DE 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.
DE 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 DE 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 DE filter is clogging up in hours or a matter of days, my first question is about the size of the DE filter, to make sure it's large enough for the pool. Hayward Perflex DE filters, or small 24 SF DE filters installed on inground pools for instance, often need extra cleaning care.
QUESTION 2: My second question is always "are you using enough DE powder?" Of course they always say they are, but remember that 1 lb of DE 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 DE powder (or Perlite Powder) - not your garden variety type of DE powder used to control insects!A one lb coffee can is the official unit of measurement. Most DE filters should use a 1 lb (32 oz dry measure) of DE powder for every 5 sq. ft. of filter surface area - for a completely clean filter, with no DE in the tank at all. After backwashing however, 30-50% of old DE is still in the tank, so you don't need so much, perhaps 1 lb of DE powder for every 8 sq. ft. of filter surface area (which is printed on the filter label).
QUESTION 3: Are you using too much DE powder? Not usually the case, but I have seen some pictures (see right) of DE filters clogged with way too much DE powder, bridging the grids.
QUESTION 4: Then I ask them if they have tried a DE filter cleaner yet? And I stress the DE part - because Sand pool filter cleaners, or the granular stuff, is too harsh for DE filter grids and cartridges. Be sure to use only DE Pool Filter Cleaner, or the Natural Chemistry cleaner, Filter Perfect.
QUESTION 5: How old are these DE grids? If they are older than 10-12 years, the best solution may be to replace your DE filter grids.
OK, that's all for now - take care of your DE filter grids, and they will reward you with sparkling pool water!