A circulating filter system requires: a pump to cause the flow, pipes and fittings to carry the flow, valves to control the flow and a filter to remove debris from the water. Pumps cause the flow of water whereas all other components resist the flow.

Hydraulic laws state that in a fitting, pipe or component containing a fluid the friction increases as the flow increases. This friction or resistance to flow is called "head" in swimming pool systems.

Swimming pool pumps have the following characteristics which are:

• Flow is directly proportional to the speed (rpm).
• Pressure (total head) is proportional to the square of the speed.
• Energy (horsepower or kilowatts) is proportional to the cube of the speed.

Therefore a drop in speed causes a small drop in flow, a big drop in head or pressure and a very, very large drop in energy consumption in kilowatts.

When a pump motor is switched to low speed, the flow is lowered by 2 (or 1/2), the head (pressure/resistance) is lowered by a factor of 4 (1/4), and the power by a factor of 6 ( 1/8 theoretically-but actually it is 1/6 due to pump design efficiencies).

Remember, that running in low speed for 24 hours is much better than running full speed for 12 hours and then shutting off the pump for 12 hours. The half speed operation insures sanitizers are evenly distributed and filtering and skimming continue, providing a clean healthy and inviting pool.

A 1-speed motor runs at 3450 rpm at high speed. A 2-speed motor runs at 3450 rpm in high speed and 1725 rpm at low speed. Since the impeller is attached to the motor shaft the pump moves about 1/2 the amount of water in low speed as in high speed operation. However, the electrical energy (kilowatt/hours) is reduced by an average of 70%.

The following information is representative of all 2-speed motors and pumps. This information is from "Century Magnetek" motors installed on Hayward pumps.

This represents an electrical savings of 70%!