Pool filters are either Diatomite or Sand

Swimming Pool Filters and Water Circulation

The ability of a system to keep a pool clean is a function of pool filter size, grade of sand or diatomite, strainer size, pipe sizes, type and number of skimmers, number of inlets, turnover ratio and characteristics of the filtration pump(pressure vs. volume). This will vary with each pool and will be conditioned by the size and shape of the swimming pool, the normal and maximum expected loadings of the pool filter and also whether it is to be an inside or outside pool.

Pool turnover rates may be from 6 hours to not more than 12 hours.

Once a pool filtration system has been designed, any one component should not be altered in capacity without considering its relationship to the capacity of other components.

A filtration pump is always selected to meet the requirements of the pool filter, ie., the normal filter rate per sq. ft. of filter area at a certain back pressure with a designed filter pumping capacity for back-washing with reduced back-pressure. If these are not mated, then continual trouble can be expected in the filtration cycle and standard of filtration.

Types of Pool Filters

The following are the types commonly used

1. Diatomite (pressure or vacuum)
2. Sand: ( a) rapid gravity (b) pressure (c) Hi Rate

Each type has advantages and disadvantages. Power costs, chemical cost and water usage, size of plant and initial cost all vary.

The gravity and pressure type sand filters are easy to operate. However, water usage is high, about 10% of the water in the pool is lost during backwash. With the diatomite and Hi Rate sand filters, only about 1% of the water is lost in backwash.

Power costs for Diatomite vacuum type and pressure sand cost about the same, whereas Diatomite pressure type filters and Hi Rate sand filters cost twice as much.