Check valves are generally installed in pipelines to prevent backflow. A check valve is basically a one-way valve, in which the flow can run freely one way, but if the flow turns the valve will close to protect the piping, other valves, pumps etc. If the flow turns and no check valve is installed, water hammer can occur. Water hammer often occur with an extreme force and will easily damage a pipeline or components.
Check valves are used in many different applications. For example they are often placed on the outlet side of a pump, to protect the pump from backflow. Centrifugal pumps, the most common type of water pumps, are not self-priming, and therefore check valves are essential for keeping water in the pipes. Also, check valves are very often used in HVAC-systems (Heating, Ventilating and Air Conditioning-systems). HVAC-systems are e.g. used in large buildings, where a coolant is pumped many storeys up. The check valves are here installed to make sure that the coolant is not flushing back down.
When choosing a check valve it is important to make a cost-benefit analysis of the specific system. Often focus is to reduce cost and at the same time obtain the lowest possible pressure loss, but when it comes to check valves a higher safety equals a higher pressure loss. So in order to make sure the check valve protects the system properly, each system has to be assessed individually, and factors such as the risk of water hammer, acceptable pressure loss, and the financial consequence of installing a check valve with a too high safety margin against water hammer have to be considered.
There are various types of check valves available for water and wastewater applications. They work in different ways but serve the same purpose.
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