Is a check valve the same as a non-return valve?

Yes. One-way valve and non-return valve are other names for a check valve.

What Is a Check Valve?

Q: What is a check valve?

A check valve lets fluid flow in one direction and automatically closes to stop it flowing back. It is also called a one-way valve or non-return valve.

Q: What does a check valve do?

It prevents backflow, protecting pumps, meters, and equipment and preventing contamination, loss of prime, and back-siphoning.

Q: How does a check valve work?

A disc, ball, or hinged flap rests against a seat. Forward flow pushes it open; when flow slows or reverses it seats and seals the valve shut. The pressure needed to first open it is called cracking pressure.

A check valve is a valve that lets fluid flow in one direction and automatically closes to stop it flowing back. You will also see them called one-way valves or non-return valves, the same device under different names. Unlike a valve you open and close by hand, a check valve works on its own, using the flow itself to open and reverse pressure to close.

What does a check valve do?

Its whole job is to prevent backflow. That protects equipment and keeps systems safe: it stops a pump from spinning backward when it shuts off, keeps treated water from mixing back into a supply, holds prime in a suction line, and prevents chemicals from siphoning back into a metering pump. Anywhere reverse flow would cause damage, contamination, or lost prime, a check valve is the simple, automatic answer.

How does a check valve work?

Inside the body is a moving part (a disc, a ball, or a hinged flap) resting against a seat. Forward flow pushes that part off the seat and fluid passes through. When flow slows or tries to reverse, the part drops or is pushed back against the seat, sealing the valve shut. The pressure needed to first open it is called the cracking pressure. Some types crack open at almost nothing; spring-loaded types need a defined pressure.

The main types

Swing check - a hinged disc swings open and drops closed. Low pressure drop, common on water and larger lines.
Spring / inline check - a spring holds a poppet closed until forward pressure opens it. Quiet, mounts any direction, good against water hammer.
Ball check - a ball lifts off the seat and reseats on reverse flow.
Wafer (double-door) - spring-loaded half-discs in a thin body that bolts between flanges, for large lines.
Y-pattern - an angled disc for low pressure drop and in-line servicing.

Each is covered in depth in Check Valve Types Explained.

Where check valves are used

They are everywhere fluid moves: pump discharge lines, chemical metering and dosing systems, water treatment, wells and sump pumps, compressed air, irrigation, and process piping. In each case the goal is the same: let flow go forward, never let it come back.

Is a check valve the same as a backflow preventer?

Not quite. A single check valve resists backflow, but code-required backflow prevention for potable water uses a tested assembly (a double check or reduced-pressure assembly) built to a standard and certified.

Choosing the right one

Pick the type for your flow and orientation, then the material for your fluid and the seal for your chemistry. Our check valve selection guide walks you through it, or compare the two most common types in Swing vs Spring Check Valve. Ready to browse? See all check valves.