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Sand Filters for Pools

Ashwini Kulkarni Sule Mar 20, 2019
Sand filters are a preferred method of water filtration in swimming pools. Read on to know more on sand filters for pools.
There are three methods of water filtration in swimming pools, Diatomaceous Earth (DE), Sand and Cartridge. Sand filters are a preferred filtration unit for household and community swimming pools.
They are inexpensive, efficient and easier to clean. Moreover, they last for at least 7 years. Sand has always been known for its ability to remove dirt and debris from water and thus purify it. Sand filters for pools use this filtration ability of sand in an effective way.

What are Sand Filters for Pools

These are specialized water filters which use sand as a medium of filtration. The sand used for this purpose is different from normal sand. A special grade #20 sand of 45 - 55 mm is used for this purpose. The filtration unit comprises large tanks which are made from fiberglass, concrete or metal.
These tanks are filled with this specialized sand. The sand bed forms the bottom layer at the base of the tank. The tank has two openings, an inlet through which impure water enters and an outlet through which clean water exits. The inlet for dirty water is situated at the top of the tank whereas the outlet for clean water is at the base of the tank.

How Do They Work

As mentioned, the sand used in sand filters is of special quality. The sand particles are tiny but very sharp. This sharpness helps in catching debris and other impurities. During water filtration mechanism, the water always flows from top to bottom.
When the dirty water enters through an inlet located at the top of the tank, the gravity pulls the water downwards, towards the sand bed. This water is made to pass through the sand bed where the debris and other impurities get trapped in the sand, whereas clean water is collected at the base of the tank.
This water is then flown out of the tank by an outlet pipe. Interestingly, the performance of this type of swimming pool filter improves after running the water through it for a few times. During initial days, the sand bed only captures large pollutants, but as the bed gets clogged with pollutants, it also traps fine particles.
However, over the time, the sand particles lose their sharpness and become rounded and smooth. This decreases their efficiency of trapping the impurities. Moreover, frequent usage leads to blockages in the sand bed, which need to be cleaned on a regular basis.
There are pressure gages located at the inlet and outlet, which are useful in determining the efficiency of the sand filter. These gages also indicate if it's time to backwash the filter.

How to Clean Sand Filters

Sand filters need backwashing once in a while. Backwashing is the reverse process of filtration which helps to remove the clogged sand bed. A pump is required to flow the water backwards in the tank. This process needs to be done manually.
The reverse flow of water loosens the debris from the sand bed and thus removes it. Backwashing must be done at least once every 2 - 3 weeks. However, if your swimming pool experiences heavy traffic or if there are large contaminants in water, you may have to do it even more frequently.
Besides, one should also change the sand in the sand bed after 3 to 5 years, depending upon the usage. The new sand improves the performance and efficiency of the swimming pool filter to a great extent. Moreover, replacing the sand is not an expensive affair.
Thus, sand filters are an economical and easy-to-implement option for water filtration in pools. Besides, they require low maintenance and provides good performance.