Why Swing Check Valves Can Be Problematic on Pump Discharge

Swing check valves are widely used due to their simple construction and low cost. However, when installed directly
on pump discharge lines, they can introduce serious reliability, noise, and mechanical stress issues.
This article explains why swing check valves can be problematic in these applications and what
alternatives should be considered.

1. How a Swing Check Valve Works

A swing check valve consists of a hinged disc that opens with forward flow and closes by gravity or reverse flow.
Unlike spring-loaded designs, the disc has a long travel distance and relatively slow closing speed.

• Disc opens fully with flow
• Closure depends on flow reversal and gravity
• No inherent damping or controlled closing force

2. Why Pump Discharge Is a Critical Location

Pump discharge lines experience rapid pressure changes, especially during start-up, shutdown,
power failure, or VFD speed variation. In these conditions, the behavior of the check valve becomes critical.

• Sudden flow deceleration when pump stops
• High inertia of moving water column
• Risk of reverse flow and pressure surge

3. Common Problems with Swing Check Valves on Pump Discharge

3.1 Water Hammer

Because swing check valves close slowly, reverse flow can accelerate before the disc shuts.
When the disc finally slams shut, it creates a pressure spike (water hammer) that can damage piping,
gaskets, pumps, and fittings.

3.2 Disc Slamming & Mechanical Wear

Repeated opening and hard closing cycles cause:

• Hinge pin wear
• Disc deformation
• Seat damage and leakage

In high-cycle pump systems, this significantly shortens valve service life.

3.3 Noise & Vibration

Disc oscillation and unstable closing can generate vibration, banging, or rattling noise,
which is often transmitted through the piping network.

3.4 Inadequate Performance at Low Flow

At low flow rates, the disc may hover in a partially open position, causing:

• Unstable flow
• Higher pressure loss
• Premature wear

4. Why Codes and Best Practices Often Discourage Swing Checks at Pump Discharge

Many engineering guidelines and fire protection standards recommend non-slam or spring-assisted check valves
on pump discharge lines to control reverse flow speed and reduce pressure surges.

While swing check valves are still permitted in some applications, designers often specify alternatives in:

• Fire pump discharge headers
• Booster pump systems
• High-rise HVAC circulation pumps

5. Better Alternatives for Pump Discharge Applications

To reduce mechanical stress, noise, and system risk, the following check valve types are commonly preferred:

• Spring-assisted swing check valves – example:
  
  UNIVAL UL/FM Swing Check Valve Datasheet (PDF)
  
• Dual-plate (double-door) check valves with short stroke
• Nozzle check valves for critical and high-velocity systems

These designs close faster, reduce reverse flow velocity, and significantly lower the risk of water hammer.

6. Summary

Swing check valves may appear attractive due to simplicity and low pressure drop, but
their slow closing behavior makes them risky on pump discharge lines.
In systems where reliability, noise control, and pressure stability matter, spring-assisted
or non-slam alternatives are usually the safer engineering choice.