De Swimming Pool Filters: An Introduction
By: Bjorn Brieman
The DE is an acronym for diatomaceous earth, and is what is found inside a DE filtration system. The first pool filters were made of sand. While there are sill high-rate sand filtration systems used in pools today, the recent innovation of DE has helped make pool filtration systems more efficient. So instead of pushing the water through a dense layer of sand, the DE filter pushes it through the diatomaceous earth (DE). The DE is composed of fossil remains that are found in the ocean. These fossils are from organisms called diatoms, which are most commonly found in Arizona and California. The DE materials is processed into a soft powder and can also be found being used for various tasks in dry cleaning facilities and even breweries.
If you were to look into a DE filter, you would see that it is made up of several grids. Each of these grids features a polypropylene cloth and can be a variety of shapes depending on who manufactured it. The common shapes are flat squares, curved pieces or discs. A manifold covers the filter and helps keep the grids in the right place. You would also see a perforated tube going through the middle of the filter, this is what sucks in the water to be filtered.
Once the filter is turned on and the water starts coming through the perforated tube, it gets pushed through the DE in each grid and any particles get trapped in the dense DE while the water cycles back out into the pool. If there is a water heater, the water will get pushed through that pipe before entering back into the pool. You will know it is time to clean out the DE filter if you see the pressure gauge on the filtration system go up. If you see it get rise between 18 and 20 psi then it is time to clean it out. If you do not do this the pressure will continue to build which could result in the particles going back into the pool or your filtration system could break. On most DE filtration systems there is a switch you can turn to set it to backwash. The filter can then be cleaned out and the DE can be replaced.
There are two different kinds of DE filtration systems. The first model uses a cloth bag that is placed inside a pressurized tank. To clean this type of filter you simply have to remove all of the DE that is full of particulate matter and then replace it with new DE. The other type uses a vacuum which has a pump connected near the return side of the filter. This model is convenient for people who use a vacuum to clean their pool. The water gets sucked through this vacuum and gets sent through the skimmer to the filter. While backwashing is not necessary with this type of filter does need to be changed when the pressure gauge exceeds 18 psi.
The key part of keeping a DE filter running efficiently is to be sure the filter contains the exact amount of DE as specified by the manufacturer of the filter. Be sure to check the instruction manual that came with the filter. If you don't have access to it, consult your local pool supply store. In some cases, the incorrect amount of the materials will cause the filter to malfunction and can even cause irreparable damage to other parts of the system. Having too much or too little DE can have an effect on the pressure inside the filter which can break the grids or cause particles to flow back into the pool. Grids can be quite expensive to replace so be sure to clean them regularly to ensure no calcium carbonate or algae begins to build up. The grids can be cleaned easily with simple soap and water and a soft bristled pool brush.