Pentair Pool DE Filter – How much DE Should I add? What is the Sq. ft. of my Filter?


DE FILTER PAD FNS PENTAIRThe owners manuals for pool equipment are wonderful things. They contain so much information and specifics about your pool equipment! The good news is if you don’t know where yours are, or if you lost it, or it got wet, you can google your make and model of equipment and find everything you need to know.

In the case of a DE Filter by Pentair, you can DOWNLOAD THE MANUAL HERE.

Here is an excerpt:

  • Filter Area: 24 sq. ft. requires 2.4lbs of de or 6 1 pound coffee cans
  • Filter area: 36 sq. ft. requires 3.6 lbs of de or 8 1 pound coffee cans
  • Filter area 48 sq. ft. requires 4.8 lbs of de or 10 1 pound coffee cans
  • Filter area 60 sq. ft. requires 6.0 lbs of de or 12 1 pound coffee cans
Your filter requires diatomaceous earth (D.E. or diatomite) for
proper filtration and operation. Your filter elements must be
precoated with this material in order to protect their surfaces
and provide the most efficient filtering action. Refer to Table 2
for the proper quantity to use with your filter. We recommend
the use of D.E. which is sold and labeled for use with
swimming pools and spas. These grades of D.E. typically
have a median particle size of 34 microns, which is ideal for
most applications.
  1. The FNS®Plus Vertical Grid Series filters are listed with the appropriate amounts of diatomite to be used to precoat the filter elements. A one (1) pound coffee can filled (level) with diatomite is equal to one half pound weight of diatomaceous earth. Do not “pack” or compress diatomite into the coffee can.
  2. Mix the required amount of diatomite with sufficient water in a bucket to make a thin, milky mixture.
  3. Follow the instructions in Section D, COATING THE FILTER ELEMENTS to introduce the slurry of diatomite into the filter.


  1. Turn the pump off, shut off any automatic controls to ensure that the system is not inadvertently started during servicing.
  2. Automatic skimmer should have Vari-Flo trimmer valve set to 100% skimmer. This will close off the main drain line. If there is a separate skimmer line and main drain line plumbed to the pump, close the main drain valve.
  3. Open the filter High Flow™ manual air relief valve, and the waste drain valve or plug if your system has one.
  4. Remove the pump’s hair and lint strainer pot lid and clean the basket. Replace basket and secure lid. Follow the instruction provided with your pump. Never attempt to assemble, disassemble or adjust the filter clamp while there is pressure in the filter. Release the tank clamp assembly and remove tank lid. Lift out the complete element for washing. Care should be taken not to lose or damage the internal air relief, located on top of the manifold.
  5. Using your garden hose, thoroughly flush off all contaminated diatomite from the filter element surfaces.
  6. After coating the stand-pipe O-ring generously with a silicone base lubricant, replace the element assembly in the filter tank, seating it firmly in place. Ensure the internal air bleed assembly is in place and free of diatomite or debris, see Section II, CLEANING THE INTERNAL AIR BLEED TUBE.
  7. Ensure the O-ring is in position in the lower tank half. Place and press the filter lid over the lower tank half sandwiching theO-ring in between.
  8. Replace tank top and carefully follow instructions in Section B,CLAMP INSTALLATION INSTRUCTIONS.
  9. Reset skimmer Vari-Flow Trimmer Valve or main drain line to pump; close waste drain valve or plug, and then follow the
    procedure as outlined in Section D,COATING THE FILTER ELEMENTS.