DE Filters – How To Service and Maintain

          Diatomaceous Earth filters also know as DE filter are a common method to filter swimming pool and spa water.  DE filters use a very fine powder to coat internal grids or plates to capture debris and dirt as they pass through a filter tank or vessel. 

          DE filter are available in many sizes usually noted in square footage.  The most common sizes are 24, 36, 48, 60 and 72 square feet of surface.  Most filters are rated at 2 gallons per minute of flow per square foot of surface area.  An example would be a 36 square foot filter would be capable of up to 72 gallons per minute of flow.  This is important so as not to attempt to use to large of a pump which could cause internal damage to the filter grids and the filter tank itself.  DE filters have been manufactured in many different materials plastic, fiberglass and stainless steel. 

          Most DE filters required a type of control valve, usually a valve known as a Multi Port Valve or a Slide Valve.  Both types of valves allow the water inside the tank to be reversed as needed to “backwash” the grids when required.  Multi port valves offer more options, such as bypass, rinse, waste, closed and recirculated modes where as slide valves usually only have filter and backwash modes.

           How does backwashing work?  Backwashing allows the reversal of the water inside the tank to flush out captured dirt and debris.  The “spent” DE is flushed outside the tank and caught in either a separation tank bag or another method for disposal.  Once the backwashing has occurred the filter will need to be re-energized with fresh DE powder.  The valve position is changed back to the filter mode and pool water is sent through the filter in the normal operating flow.  The skimmer valve of the pool is opened and fresh DE powder is added to the filter through the skimmer allowing the pump to pull the powered back into the tank and allowing the grids or plates to be recoated.

          Will the filter need to be disassembled and cleaned at some point in time?  Yes, backwashing the filter will only be effective a certain number of times.  Shorter and shorter filter runs will be noted and this will signal that the filter will need to be taken apart and completely serviced.  Servicing a DE filter will require removal of the internal grids or plates, cleaning of their surfaces, flushing out of the tank, reassembly, and addition of fresh filter powder directly inside the filter.  Remember to lubricate o-rings before reassembly to allow for water tight seals.

           How much DE will need to be added to a filter?  Filters which are produced in various square footage sizes and will require a certain number of pounds of DE per square foot of filter area.  Consult your filter owner’s manual for manufactures recommendations.

           Please keep in mind to use caution when working with Diatomaceous Earth, eye and nose protection along with gloves should be used when ever working with or handling DE.