How to Prevent Water Hammer in Commercial Water Heating

How to Prevent Water Hammer in Commercial Water Heating Systems

Every commercial plumber and facility manager knows the dreaded “bang” echoing through a boiler room. That sound isn’t just an annoying quirk of a building’s piping; it is the sound of hydraulic shock actively damaging your equipment.

When it comes to commercial water heater maintenance, ignoring water hammer is a recipe for disaster. Let’s break down exactly what causes it, the risks it poses to your high-efficiency systems, and the simple startup steps you can take to prevent it.

What Causes Water Hammer?

Water hammer (hydraulic shock) occurs when water flowing through a pipe is suddenly forced to stop or change direction. Because water is largely incompressible, that kinetic energy has nowhere to go. It sends a high-pressure shockwave crashing back through the piping system.

In commercial plumbing systems, this is typically caused by:

Fast-acting solenoid valves closing too quickly.
Pumps shutting down abruptly.
Human error during system startup (opening valves too fast).

The Hidden Risks to Your Equipment

You might hear a loud bang, but the real damage is happening where you can’t see it. The pressure spikes from water hammer can easily exceed the design limits of your pipes and commercial tankless units.

If left unaddressed, water hammer will cause:

Ruptured pipes and blown fittings.
Damaged heat exchangers and internal flow sensors.
Premature wear on pressure reducing valves (PRVs).
Expensive facility downtime and flooded mechanical rooms.

Best Practices for Opening Inlet Valves

The most common, completely avoidable cause of water hammer happens right at startup or after a maintenance shutdown. When bringing an Intellihot commercial water heater (or any boiler) back online, patience is your best tool for water hammer prevention.

If you open the main water inlet valve too fast, the sudden rush of high-pressure water slamming into empty pipes and internal components will cause immediate shock.

Watch this quick tip from our startup series on exactly how to introduce water back into the unit:

Additional Water Hammer Prevention Strategies

While proper valve operation is critical during startup, your overall system design must also account for pressure spikes during daily operation.

Install Water Hammer Arrestors: These act as shock absorbers. When a pressure wave hits, the air bladder inside the arrestor compresses, absorbing the destructive energy before it reaches your water heaters.
Monitor Water Pressure: Ensure your incoming city water pressure isn’t too high. Install and maintain a Pressure Reducing Valve (PRV) to keep system pressure within safe, manufacturer-recommended operating limits.
Bleed the Air: Always purge air from the system completely during startup using the bleed screw and T&P valve, as trapped air bubbles can exacerbate pressure fluctuations.

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