DE filters are a bit more complex than sand or cartridge filters, but they do provide slightly better filtration as well as some other benefits. The purpose of this article is to describe how a diatomaceous earth filter operates.
In a standard diatomaceous earth filter, the water flows into the filter through the inlet port. It is then passed through the filter grids. The grids are plastic frames covered with a woven polyester fabric.
The grids are coated with DE (diatomaceous earth). Water passes through both sides of the grid and passes out through the neck of the grid. As water passes through the DE on the surface of the grids, particles of debris are trapped between the particles of DE and also within the particles of DE, which are actually porous.
The grids are all fitted into a manifold at the top of the grid assembly (or at the bottom on a SMBW filter). The water passes through the manifold and back out the outlet pipe of the filter. The filter has an air bleed tube inside that will bleed off almost all the air that builds up inside the filter.
There is also a manual air bleed on the top of the filter that can be used to bleed off the air or to let air into the tank when you are preparing to take the filter part (after you have turned the pump off).
There is a pressure gauge on the top of the filter. When installing the filter, or when putting it back together after cleaning, you should make sure that the face of this gauge is visible to you when you are turning the equipment on and off so you can see any dangerous rise in pressure.