CVN, CVP and CVK Series Check Valves Product Spotlight

Take a look at one of our miniature low-pressure diaphragm check valves

A product overview of one of ISM’s popular product series

Watch this short video overview about these precision molded diaphragm check valves >> 

Compact, low-pressure plastic diaphragm check valves are useful for a wide variety of applications. Their small size, low weight, durability and broad chemical compatibility makes them versatile choices for non-critical low-volume air, gas and liquid backflow prevention.

These USA-made check valves are assembled using sonic welding for exceptional toughness and durability. The series provides an economical and reliable diaphragm check valve option without sacrificing quality.

Compact check valves with a choice of connections

  • 1/8-inch male NPT thread to hose barb
  • Uniform (same-size barb to same-size barb)
  • Enlarging (smaller-size barb to a larger size barb)
  • Reducing (larger-size barb to a smaller-size barb)

The hose barb inlets and outlets sizes of these check valves range from 1/8 inch to 3/8 inches (1/8, 3/16, 1/4 and 3/8 inch). The 1/8-inch male NPT thread inlet option comes with this same range of hose barb sizes on the outlet end also.

A raised triangle flow indicator molded into the body of a C V N, C V P, C V K series plastic diaphragm check valve.
Flow direction on a CVN,
CVP, CVK series check valve

An important installation note
Check valves need to be oriented correctly to function properly. Flow direction on the CVN, CVP and CVK series check valves is indicated by a raised triangle molded into the check valve bodies.

What does precision molded mean?These fittings are precision molded using proprietary technology that eliminates parting lines on the hose barbs. No parting lines on the barbs means there is no potential flash or mismatch. The sealing surfaces of the hose barb are entirely seamless.

Hose barb critical sealing surfaces

  • the barb ridge
  • the barb slope
  • the barb shaft or shank

Hose barb connections with no potential leak paths between the sealing surfaces of the hose barb and the flexible plastic tubing provide the best leak-proof seals.

Get some insight into hose barb design and how this can affect your application >>

A C V P series three eighths hose barbed diaphragm check valve.
CVN, CVP, CVK hose barb
by hose barb check valve

Nylon, polycarbonate, Kynar® (PVDF) or polypropylene body material

  • Kynar® (PVDF) is a tough, stable and very non-reactive engineered plastic.
  • Polycarbonate is hard and transparent with moderate chemical resistance and good impact resistance.
  • Polypropylene is especially economical plus it is highly resistant to solvents and chemicals in harsh environments.
  • Nylon provides good durability and chemical resistance along with low permeability to gases. It also performs well at elevated temperatures.

Learn more about Kynar® (PVDF) plastic >

Silicone, Viton® (FKM) or neoprene diaphragm material

  • Silicone rubber is very durable and retains its flexibility in extreme heat or cold.
  • Viton® (FKM) rubber is resistant to a wide variety of chemicals and fluids, even at high temperatures.
  • Neoprene is a strong general-purpose rubber with excellent abrasion resistance and good resistance to chemicals.
A C V P series eighth inch N P T by quarter inch hose barb diaphragm check valve.
CVN, CVP, CVK series
NPT thread by hose barb check valve

Very low cracking pressure
The CVN/CVP/CVK check valves have a very low cracking pressure: 6 inches H2O (water). This is equal to only 0.015 psi or 1.49 kPa (kilopascals).

Find out more about cracking pressure and the challenges of choosing cracking pressures for low-pressure applications >>

What is “inches of water”?When talking about pressure measurements, inches of water is pretty much what it says. One-inch of water is the pressure exerted by a one-inch high column of water under very specific, defined conditions. Atmospheric pressure, 1 standard atmosphere, is equal to about 407 inches of water.

Inches water or inches of water is used for measuring very small pressure differences. It is a measurement unit primarily used in the United States because it non-metric.

A typical plastic diaphragm check valve in both an exploded and a cross section view.
Typical diaphragm check valve

Get tips and insights about check valves and how they workCheck valves, non-return or one-way valves, allow liquid or air to flow in only one direction. Manufacturers make them in a wide range of sizes and types. Tremendous varieties of applications use them to prevent costly or even dangerous backflow.

Even though check valves are widely used for everyday applications, the how and why of check valves and their different designs is not always well understood. Here is some additional information about check valves from the ISM blog:


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A C O P series spring assisted or spring loaded check valve with a cross section view.
COP series brass check valve
with a cross section view

Some other, related blog posts

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Are you developing a design for or maintaining a low-pressure (less than 125 psi, 8.6 bar) small-bore air, gas or fluid system? Then ISM has the valve for it.

Get a catalog and find out more about the miniature flow control and fluid management valves we carry >>

Front cover of the ISM Miniature Flow Control Valves catalog. Click here to get the catalog.
The ISM Miniature Flow Control Valves catalog includes

  • Product specifications
  • Photos and rendered CAD images of the valves
  • Links to product pages in our e-commerce catalog


Check out our complete lineup of miniature flow control valves >>

Keep in mind we carry thousands of miniature flow control valves. Plus, thousands of related products like connectors, adapters, gauges and so on.

Get the catalog


Learn more about the different types of miniature flow control valves you can get from us >>

A sample selection of the types of miniature flow control valves carried by ISM.

Diaphragm Check Valves  |  Spring Loaded Check Valves  |  Duckbill Check Valves  |  Plastic Push-In Check Valves  |  Ball Check Valves  |  Piston Check Valves  |  Poppet Check Valves  |  Modular Check Valves  |  Plastic Ball Valves  |  Brass Ball Valves  |  Stainless Steel Ball Valves  |  Needle Valves  |  Metering Valves (Needle)  |  Metering Valves (Flow Control)  |  Button-Pilot-Shuttle-Toggle Valves  |  Stopcocks  |  Plastic & Metal Relief Valves  |  Regulators  |  Pinch Valves