The material placed inside the swimming pool sand filter is there to trap oxidised matter and debris from the pool water.
Filter sand has been sifted to a granular size of (silica sand; 0.8 – 1.1 mm) is specially graded to trap particles in the 20 – 100micron range. Weekly backwashing releases the dirt to drain allowing the filter media to continue its filtering process.
How often should the sand in a swimming pool filter be changed? We recommend changing the sand every 18 months to 2 years.
The roughness of filter sand makes it very efficient in filtering out dirt particles. Over time, the sand wears down and becomes smoother, and the filter loses efficiency.
There are three major types of pool filtering system: cartridge, sand, and diatomaceous earth (DE). Sand and DE filters use a multiport valve primarily to help clean or backflush the filter media. A typical multiport valve has 6 settings: filter, backwash, rinse, waste, closed, circulate/bypass. This guide explains the function of these setting and shows how they circulate water in a typical sand filter.
Cartridge filters do not have multiport valves. These filters are cleaned by removing the cartridge and spraying it with a garden hose.
THERE ARE 6 SETTINGS ON A MULTIPORT VALVE
The normal setting for the valve. Pool water is drawn through the pump, passed into the top of the filter tank and down through the filter media, via the filter under drain system, after which it is returned to the swimming pool.