About Check Valves
In plumbing applications, check valve is often used to prevent the cross-contamination of water due to back pressure or back-siphonage, often caused by drop in pressure on the supply side or by draining the system.
In heating applications, check valve acts as a one-way valve to prevent mixing of the supply and return water, especially in systems with radiant floors and baseboard/panel radiators.
Difference between Swing and Spring Loaded Check Valves
Swing type check valve (also commonly called "swing check") has an internal brass flapper suspended on a shaft. When looking at the picture of the swing check, the shaft end is visible (brass hexagonal bolt head). In a horizontal position (as shown on the product picture), the flapper is in vertical position and closes the opening. When water starts to flow from the inlet, it pushes against the flapper and, with no resistance, opens it. It water is pushed backwards, the flapper return to the original positions, sealing the opening. Because of the nature of the design of the swing check valves, they should only be used on horizontal pipe runs, as level as possible.
Spring loaded check valves have a brass flapper with rubber gasket, which is secured on the shaft/stem located at the center of the valve and running parallel with the water flow. A steel spring inside the valve pushes the flapper against the opening with small force, ensuring that no water is flowing due to gravity. When water begins to flow, it pushes against the flapper and opens it with minimal resistance. In case of a backflow, the spring quickly pushes the flapper back in place, which immediately stops the flow. Unlike swing type, spring check valves can be installed in any position - horizontal, vertical or anywhere in between.
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