Types Of Check Valves
There are several different types of check valves available and they have specific applications. Spring-loaded, stem or cage poppet-style check valves should be used with submersible pumps.
These types are designed to close quickly as water flow stops and begins to move in a reverse direction when the pump shuts off. Swing-type check valves are not appropriate for this function because they react too slowly. In order to be effective for this application, your check valve needs to work quickly. When the pump stops there is a sudden reversal of flow before a swing valve has time to close. This can cause a sudden change in the velocity of the water creating a water hammer.
The size and installation of your check valve is crucial. They must be properly sized to meet the pump's flow and pressure conditions. The pressure rating of the check valve should exceed the maximum output pressure of the pump. The best solution is to consult with your well water professional. They can make sure you have the proper valve for your well and that it's installed correctly.
Conditions Controlled By Your Check Valve
Along with holding water pressure in your system, your check valve assists in the smooth and safe operation of your water system by extending its life and preventing backspin, up-thrust and water hammer. Here are a few conditions check valves help to control.
With no check valve or if yours fails, the water in the drop pipe and system will flow back when the pump stops. This can cause the pump to rotate in the wrong direction as the water returns to the source. If your pump motor starts while this is in progress it would place a heavy strain that may cause the pump shaft to break or the motor thrust bearing to be damaged.
With no check valve or a leaking valve, the water would drain back into the well like backspin. The pump would the start under a reduced head condition potentially causing an up-thrust on the impeller/shaft assembly. Repeated up-thrust at each start can cause premature wear and the failure of either the pump, the motor, or both.
Water flowing through your plumbing system has weight and velocity (kinetic energy). When the pump stops, the water continues to move. Its energy must be absorbed somehow. The pressure tank normally performs this function. However, if your system has leaking, slow-acting or too few check valves, the water will reverse direction. When it stops the rapid dissipation of energy can cause a water hammer. This water hammer can have enough force to split pipes, break joints and damage the pump.