Every pool needs to have a filtration system. Basically the filtration system pumps water from the pool, via pipes, to a filter, and then through a return line, which may or may not include a heater, to the pool. The filter removes sediment, debris and dirt particles, handling the cleaning that pool chemicals cannot. Various types of pool filters are available, including cartridge filters, high rate sand filters and diatomaceous earth filters.
High Rate Sand Filters
This type of filter consists of a container with a layer of sand inside through which water is continuously filtered. Dirt and debris is trapped in the sand until it builds up to the point that water flow becomes restricted. A pressure gauge is monitored until it indicates that backwashing is required.
Backwashing is when the water flow is reversed, by means of turning a control valve, and the dirt and debris trapped in the sand is washed loose out into a waste dump line.
It is important to use the correct sand that the manufacturer specifies for a high rate sand filter; unless you have the exact right particle size, the filter will be less effective. You should also follow the recommendations for how deep a layer of sand to add; not enough sand and you will have to backwash the filter more often.
Since the sand doesn’t reach it’s maximum filtration ability until a certain amount of dirt has built up in it, backwashing too frequently is not going to help you attain cleaner pool water.
Diatomaceous Earth Pool Filters
This type of filter is the most widely used for residential swimming pools. It uses diatomaceous earth, chalky, fine powder derived from fossilized remains of diatoms, tiny sea organisms, as it’s filtering media. A diatomaceous earth filter consists of a tank within, which are arranged grids covered with Dacron or polypropylene around a circular pipe with perforations in it.
Water is pumped from the pool to the filter tank, where it moves through the grids of cloth, into the central pipe and then back to the pool. The diatomaceous earth is mixed with water to form a slurry, which is put into the pool’s skimmer box; the slurry gets drawn into the filter, where it build up a fine layer on the grid cloth and becomes a filtration media.
Like high rate sand filters, these types of filters also build up dirt and debris on the filtration media until water flow is impeded and backwashing is required. During backwashing, water flows out from the center pipe and washes the diatomaceous earth and accumulated dirt off the cloth grids, it is then washed out into the waste line, and finally, more diatomaceous earth is added through the skimmer box.
It is important to add the proper amount of diatomaceous earth, as adding too much or too little can damage the cloth grids. Follow the manufacturer’s recommendations. The cloth grids should also be removed and cleaned periodically to get rid of calcium scale, impacted dirt and accumulated body oils.
Cartridge Pool Filters
Cartridge filters consist of an enclosed tank that contains an inner replaceable cartridge with corrugated filter paper or polyester cloth inside. No backwashing is required on these types of filters, but you do need to take the cartridge out of the tank and wash it off with a high pressure hose when it becomes too dirty, as indicated by a pressure gauge.
The lack of backwash capability in cartridge filters is actually an advantage, since you will be conserving good heated and chemically balanced water that otherwise would be dumped into the waste line. Cartridge filters do not have to build up a certain amount of debris and sediment in order to hit their maximum filtering efficiency, they are effective from the moment their first use.