Check Valves: Controlling Flow Direction

 

Hayward's check valves are available in PVC, CPVC, GFPP and PVDF materials.  There are six distinct product families of check valve styles to choose from depending upon your application requirements.

 

When to use a check valve?

Check valves are typically installed to prevent the reversal of flow in a piping system where pumps or filters are installed.  Sometimes check valves are used to maintain fluid and pressure within sections of a piping system.  An example of this would be to help maintain the prime within a pump.  Check valves also help protect all piping components from excessive water hammer during pump start-up or initial filling of the pipeline.

 

There are four types of check valves:

1. Ball check valves are used for non-viscous and clean fluids where there will be some system backpressure (≥2 PSI) to ensure proper operation. 

2. Y check valves are used for dirtier fluids and fluids having higher viscosities.

3. Full body style swing check valves are used for larger piping systems and support maximum flow rate through pipelines; they can also be fitted with limit switches for position indication..

4. Wafer check valves are also used for larger piping systems and high flow rates, especially when there are space restrictions or when the liquid contains solids which might foul a full body style swing check valve.

Some check valves are available with a spring assist, for applications that have low backpressure, dirtier fluids and for applications that benefit from quicker closing.  Refer to models SLC, WCV and WC which offer this optional feature.

 

Hayward's design advantage is an all non-alloy construction; for the models that use a spring, the material of construction would be either 316SS or Hastelloy.

 

Ball Check Valves

Hayward's TC model ball check valves have a true-union body design to simplify installation and maintenance.  Reliable operation occurs without any needs for adjustments or settings.  The line pressure moves the solid plastic ball off of the EPDM or FKM seat.  When flow stops, the system back pressure pushes the ball against the seat stopping the flow. The ball is free floating, so it never seats twice in the same position, preventing uneven wear.  Key features compared to other designs include that the ball is retained with the true union nuts removed and the ball is safety blocked.

 

Y Check Valves

Hayward's Y check valves are available with or without springs and their bodies with either standard or true-union designs.  An advantage of Y check valves are that they can be installed in any position and work well with dirtier fluids.  The Y design enables servicing in-line and the spring loaded models can be set to open within 2 ≥ 15 PSI.  A common application for Y check valves are preventing loss of process fluid through spray nozzles once the pump is turned off.  Another common application is as an anti-siphon valve when the process line is below the fill level of the feed tank of a pump system.

 

Swing Check Valves

Hayward's swing check valves have a truly unique and innovative design: each half of its body is identical.  Therefore, if one seat wears or becomes damaged, you can reposition the valve in your pipeline after adjusting the clapper and it's like having a whole new valve!  Swing check valves are often used for slurries or liquids that would otherwise damage valve seats.  Another great feature of the SW series swing check valve is the built-in o-ring flange seal, eliminating the need for separate flange gaskets.  Hayward's swing check valves can operate at nearly twice the pressure and temperature rating of competitors valves and only require ≥3 PSI for positive sealing.

 

Wafer Check Valves

Hayward's wafer check valves are available with or without a spring.  The WCV series is available in 2" to 8" sizes and are a full pattern design, requiring no spacers or special flange for full flow rate and designed for both ANSI 125/150 and DIN/PN10 flanged pipelines.  The WC series requires a spacer for unrestricted flow and spacers are provided with the valves through the 8" sizes; spacers for sizes up to 24" are available for an additional cost.  The big advantage for wafer check valves is their compact size and high flow coefficient value (minimal pressure drop).  These are low cost check valves for high flow rates that are lightweight and easy to maintain.  Spring assisted wafer check valves are typically used for pulsating flow applications and horizontal piping where quicker closure is desired to minimize backflow or water hammer.

 

Check Valve Installation Considerations

When installed downstream of a pump, install at a distance of at least 10 pipe diameters from the pump outlet and at least 5 pipe diameters from the nearest elbow or tee.

 

Additional Resources

• Download Hayward’s complete Engineering Product Guide for additional selection criteria, such as flow coefficient values, water hammer calculations and other technical formulas.

 

Additional Resources (PDF files)

• Chemical Compatibility Charts

• Operating Temperature Charts

• Description of Materials

 

Connections

Threaded connections are NPT (American Standard) tapered pipe threads and it is suggested that a non-petroleum based sealant such as PTFE (Teflon™) plumbers tape is applied to your inlet/outlet pipe connections.

 

Flanged connections conform to ANSI 150# dimensions and a 1/8” thick full face gasket having a durometer rating between 50 and 70 is required for proper sealing for models that do not have a integral flange o-ring.

 

If you are not sure which check valve is most appropriate for your application, send us an inquiry, we typically reply quickly, certainly within 24 hours.