A check valve is an important part of every HVAC design and any application that needs flow control. In fact, it has a mechanism that opens and closes to control the flow of fluids. To prevent expensive damage to a system,  HVAC engineers, choose the correct check valve and know how they work. They’re used to protect equipment from backflow, prevent contamination caused by reverse flow, prevent siphoning, and keep a vacuum seal. Used in almost every industry, they’re built into things like furnaces, boilers, gas systems, vacuum systems, and many more! Valves like any HVAC system need their own maintenance. 

What is a check valve, anyway? To learn more about their types and how they work, keep reading!

What Is a Check Valve?


Check valves restrict the flow of fluids to one direction by using two ports: one is the inlet (or intake) and the other is the output. They’re called a “one-way check valve” or “non-return valve”. The media (ie. gases, liquids, or steam) flows one way due to pressure differentials.

Check Valve Types

We’ve answered your question, “What is a check valve?”. Now let’s get into their different types. Flow control is necessary for media injection, isolation, priming pumps, and maintaining pressure, and several other applications.

1. Low-Pressure Relief Valves

If you need a valve for a low-pressure application, use an inline spring-loaded check valve. Springs can be built to specifications depending on the properties you need the material to have. Both your pneumatic and your water valve can be custom-built.

Seals on low-pressure relief valves will be either metal-to-metal, elastomeric, or thermoplastic. The poppet separates from the valve seat as the upstream pressure applies force. Know the maximum and set pressure so it doesn’t overwork the system.

Vacuum Breakers

Check valves can be used as vacuum breakers, allowing air into the pipe system and subsequently blocking the flow of media. The vacuum type will need to be installed at the system’s uppermost section. This will relieve the vacuum while pumping down or during thermal applications.

2. Spring Loaded Y

The spring-loaded Y valves have a spring and movable disc at an angled position. This creates the “Y” shape. The great thing about this shape is that it can be inspected while the system is running. The downside is that they’re larger than the others.

3. More Check Valve Types!

Keep your system in check by buying the correct type for the job. Do your research on all types thoroughly so it doesn’t cause damage. Asking a professional for their opinion is best so there are no questions left unanswered prior to installation.

  • Spring-loaded in-line
  • Ball
  • Diaphragm
  • Lift
  • Swing
  • Stop
  • Butterfly/Wafer
  • Duckbill
  • Foot
  • 2 check valve (2-way)

When choosing, consider material compatibility, connection point size, max pressure, cracking pressure, and orientation. Know envelope dimensions, temperature (of media and external), and accessibility for aftermarket services. After-market services should include inspection, maintenance, repairs, the provision of parts, and digital services.

Know Your Check Valves!

Knowing all the details of your system will help prevent major problems. Getting the perfect check valve will ensure efficiency within your HVAC system. Start with top quality check valves from the get-go. Lastly, we hope we answered your question, “What is a check valve?” so you can get closer to starting that project!

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In case you need any assistance regarding your architecture or structure or HVAC design requirements,  feel free to contact us!