Hot Tub Filters page 4

Like cartridge filters, DE filters are sized by the square footage of surface area of their filtration media. In DE filters, therefore, the total surface square footage of the grids is the size of the filter. Typically, there are 8 grids in a filter totalling 24 to 72 square feet (2 to 7 square meters), designed into tanks of 2 to 5 feet (60 to 150 centimetres) high by around 2 feet (60 centimetres) in diameter. Obviously the larger the filter, the greater the capacity it will have to move water through it. Therefore, filters are also rated by how many gallons or litres per minute can flow through them.

Sand Filters

Another filtration medium is common sand, which is the natural method of filtering water. For hot tubs, the most common sand filter is the high-rate sand filter, and it is quite simple to understand.

Water is passed through a layer of sand and gravel inside a tank, which strains impurities from the water before it leaves the tank. As with filters, the water is under pressure inside the tank from the resistance created by trying to push it through the filtration media. This differentiates it from another type of sand and gravel filter, used especially in fish ponds where there is no such pressure, the free flow sand filter. Since free flow sand filters are not typically used for hot tubs or hot tubs, these will not be discussed further.

A hot tub equipment package that includes a sand filter, water enters the tank through the valve on top and sprays over the sand inside. Water runs through the sand, with the impurities being caught by the sharp edges of the grains, and is pushed through the manifold at the bottom where it is directed up through the pipe in the centre and out of the hot tub filter through another port of the valve on top. The individual fingers of the drain manifold are called laterals, and the centre pipe used to return clean water is called a stanchion pipe. To drain the tank, a drainpipe is provided at the bottom as well.

Like other types of filters, sand filters are sized by square footage (or square meters) and the resulting ability of the unit in gallons or litres per minute. Knowing the volume of sand recommended for any given filter (expressed in cubic feet), the manufacturer will arrive at a square footage (or square meter) value and a resulting gallons or litres per minute rating. Sand filter tanks are usually large, round, fibreglass units, between 2 and 4 feet (60 and 120 centimetres) in diameter.