How Do I Choose a Check Valve?

In order to be able to select the right check valve for your application, you should consider a number of selection criteria. First, there is no one type of check valve that is the best choice for all applications, and different selection criteria may not be equally important for all situations.

Some of the things you need to consider are fluid compatibility, flow characteristics, head loss, non-impact characteristics, and total cost of ownership. In order to get the best performance, it is certainly important to select a valve based on the characteristics of each particular installation.

When selecting a check valve, the following series of questions can help determine the application requirements and find the proper size and type of check valve needed.

What is the flow rate or expected flow rate of the system (GPM)?

What is the pressure at static and pumping conditions (PSI or FEET)?

What is the pipe diameter size?

What is the media (potable water, wastewater, slurry, etc.)?

What are the potential chemicals that will be used in the system?

What size solids will the system handle (if any)?

Is it a multi-pump application?

Is it a title system?

Where and how far (in feet) is the discharge line?

Is the discharge line open or closed?

Check Valve

Some selection criteria to consider when choosing a check valve

Total Cost of Ownership

The cost of a check valve may be more than just the purchase price. For some installations, the most important costs may be purchase and installation, but in other cases, maintenance or energy costs may be equally or even more important. Therefore, when using cost as a selection criterion for check valves, the total cost of the valve over its entire service life should be considered. In general, the simpler the valve construction, the lower the maintenance requirements. Both swing check valves and ball check valves are very cost effective.

Fluid

All check valves are designed to handle water and treated wastewater, but handling raw wastewater/sewage can cause some problems. When selecting a valve for these fluids, you should probably consider how the presence of solids may affect the operation of the valve.

Flow Characteristics

If a check valve closes very quickly, it may stop the thumping sound. However, closing quickly does not prevent surges caused by pump start-ups and shutdowns. If the valve opens (and closes) quickly, the flow rate will change abruptly, making it more susceptible to surging.

Head loss

Head loss is a function of fluid velocity, and valve head loss is influenced by system flow conditions and the valve's internal surface. The geometry and closure design of the valve body determines the flow area through the valve and therefore also affects the head loss.

The head loss to be considered is a combination of static head (caused by height differences) and frictional head (caused by the pipe and valve internals). There are many formulas for head loss and valve ratings based on this. Probably the most common is the flow coefficient of the amount of water passing through the valve at a certain pressure drop over a certain period of time. However, for comparison purposes, the coefficient of resistance, Kv, is considered to be the best choice.

Both spherical check valves and swing check valves have low head loss.

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