by Sean Griffin, March 24, 2010
D.E. Pool Filter Grids Care & Repair
Enclosed within every swimming pool filter there lays a means to extract unwanted contaminants while allowing cleaner water to return back to the body of water. The three most common swimming pool and spa filters in use today are the cartridge, sand, and D.E. (diatomaceous earth) pool filters. Each utilizes a different media to remove unwanted particles. The Cartridge filter uses a pleated paper filtering element which catches small particles. These cartridges are removed and manually cleaned.
The sand filter makes use of a sand bed where water is dispersed through the sand which holds the impurities while allowing water to re-circulate. To remove them the flow of water is reversed, flushing out the dirt in a process called “backwashing”. Sand becomes eroded smooth and loses surface area and needs to be replaced every 5-7 years. In a D.E. Filter, you also reverse the flow of water to backwash. D.E. systems differ in that the media (diatomaceous earth) needs to be replenished after being flushed out along with filtered particles.
Diatomaceous earth is mined and is the fossilized exoskeletons of tiny diatoms. They are used to coat “grids” in the filter housing and act as tiny sieves to remove debris. They are very small and because of their large surface area they can filter out particles as small as 5 microns. D.E. commonly comes in powder form and is introduced through a skimmer. The size of the initial charge of D.E. depends on the filter model and size. The D.E. coats the individual grids increasing the surface area to filter the water.
Filter pressure is noted when the filter tank is originally charged with DE pwder, and the pool is operating without restriction. Once pressure builds up 7-10 psi above the start up or base pressure, backwashing is indicated. Filters are backwashed utilizing a special valve. Common valves include the push/pull or slide valve and the multiport valve. The frequency and length of backwashing depends on numerous factors to include the size of the filter (the larger the surface area the less you will need to backwash), contaminants introduced into the water and condition of equipment.
Over time and after several backwashing procedures you may notice afterward that the filter pressure did not drop to it's lowest level. This can be due to D.E. clogged up within the grid assembly, "bridging" between grids, oil or mineral clogging of the fabric on which the D.E. sits, or from having too much DE. From time to time you will need to manually clean out your filter grids and inspect all of the correlating components.
Exact procedures vary from model to model but here is a broad overview of how to clean and inspect your de filter grids:
- Turn off power and ensure timers are not set to turn on any pump as you will be disassembling a pressurized component.
- Close or direct any valve(s) to prevent flooding and/or loss of prime. Isolate filter.
- Relieve any existing pressure within filter. This can be achieved by a manual air relief valve on top..
- Disassemble filter accordingly, usually by removing the clamp band assembly and lifting the lid straight up.
- In some cases filter grids can be cleaned while still in filter body by removing top half of filter tank and removing the filter drain plug. You will need good water pressure and drainage at equipment pad. This saves water and gives a much better cleaning, and allows you to dispose of the DE filter powder, which can be damaging to streams, plant life and animals.
- If cleaning grids while in tank isn't working for you, remove the grids for cleaning. Usually a filter grid assembly can be removed by grasping the manifold and pulling off of standpipe. Good water and a high pressure hose nozzle can handle typical D.E. build up.
- For stained filter grids you can soak with a mixture of muriatic acid and water. Concentration and varies. One to four, acid to water mixture is a common ratio to clean filter grids. Acid washing grids will remove mineral build up, but not oily build up. Use a pool filter cleaner product, TSP or pool enzymes to remove oily buildup on de filter grids.
- Inspect all components for any tears or rips, especially at the seam. These can be sewn together, or if many grids are torn, it may be best to replace the de filter grid set. DE grid sets come 7 large and 1 small grid and are measured by their height, 12", 18", 24", 30" and 36".
- Reassemble filter clamp band carefully and properly. Open air bleeder, any closed valves, turn on pump.
- Add DE filter powder immediately, through the skimmer. Use a 1lb coffee can sized scoop for every 4" of grid height.
Filter grids assemblies, to include the manifold, collector, and grid set, are subject to constant water pressure along with the possibilities of corrosive water chemistry. The fabrics on the skeleton of the individual grids can fray and can eventually tear. Over pressurized filters can also experience grids that will collapse. Pressure can also crack and destroy the top manifold. Filter grids should be purchased according to the make, model, and size of your filter.
For those unsure of the size model they own, the height of a grid can be doubled to indicate square footage of model in most cases. Replacement grids are sold individually or in a set. When grids are purchased this way the homeowner will need to reconstruct the grid assembly. To make internal filter repair more simplistic, some models offer complete grid assemblies or complete filter element clusters which allows basic swapping out of insides.
If your filter body has been damaged or your unit is outdated you have plenty of options as far as upgrading your filter in its entirety. For a handy comparison chart take a look at our pool filter comparison page.