What is a demand pump?

Demand pumps, also called delivery pumps, are used to transport water from a storage tank to the point of distribution. Demand pumps depend upon the user to indicate a demand for water. The user may push a button to indicate a desire for water, which activates a solenoid to open closed valves in the water line. When the pump senses open valves, it turns itself on to supply water. The pump turns itself off again when it senses pressure building in the delivery line due to closed valves.

Demand pumps have many common applications, including sending water from a non-pressurized tank to a water fountain, increasing water pressure from an undersink reverse osmosis unit to a refrigerator water dispenser or ice maker, or for larger-scale application such as supplying a car wash.

Users interested in installing a demand pump should also consider adding a pump tank to their set-up. A pump tank ensures that the correct degree of constant back pressure is applied against the pump’s pressure switch, which prevents the pump from constantly cycling on and off to renew pressure. Installing a pump tank also provides extra water storage and protects appliances and downstream plumbing from the shock of sudden pressure surges.

What is the difference between bypass pumps and demand pumps?

The user may choose to use either a demand pump or a bypass pump depending on the intended application. Demand pumps are ideal for hand-held spray wands because they allow the ability to move fluids with set flow and pressure requirements. While demand pumps shut off once the pressure in the system indicates that the fluid demand has been met, bypass pumps continue to run regardless of the pressure in the system. A bypass pump may be chosen for use with a spray bar that contains several different nozzles that are controlled independently due to its ability to bypass excess flow when nozzles are turned on or off.

Demand, nor bypass pumps, should be used to pump gasoline, kerosene oil, or other flammable fluids.