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How To Shield Irrigation Systems From Water Hammer

By David Olson on June 29, 2016 in BlogNo Comments

How To Shield Irrigation Systems From Water Hammer graphic

Water hammer. Surge. Dry line shock. These sound like spells cast by a wizard in a video game. But they’re actually names for a real event that can harm the irrigation systems you manage.

There is no silver bullet solution to totally prevent water hammer, but you can reduce the chances of it happening, and also mitigate its impact should water hammer appear in your system.

What is water hammer?
Water hammer can occur when you are opening or closing valves, or starting or stopping pumps. It’s the shock wave created by a surge of water, moving in empty pipes at a velocity of up to 5 feet per second, that stops abruptly inside the system. It’s like a bus driving at full speed into a wall.

The shock wave moves back through the system, rattling pipes as the energy in the water transfers to the pipes themselves, seeking relief. It will reach the valve with a loud bang or thump—hence the name water hammer.

Why worry about water hammer?
With the shock wave is an enormous spike in water pressure, or surge. This surge lasts less than a second, but it can do lasting harm to a system as each occurrence wears out pipe and loosens fittings. This will eventually cause leaks, and cost you time and money in repairs that could have been prevented.

What can you do about water hammer?
There is no magic cure for water hammer. But you can take steps to reduce its impact, and Ewing can help. Here’s how…

Clear the air to prevent water hammer from occurring
You can’t always stop air from entering the system. But you can carefully control how you expel the air from it to reduce dangerous velocities.

For example, when you turn on a system in the spring, first remove the furthest head on the line to allow air to bleed out. Then fill the pipes slowly to avoid trapping air.

Even the best-designed system can have air inside it. Air in the system can contribute to water hammer, as it can travel at a higher velocity than water. When the system is turned on, the water behind the air bubble will speed up, the air will run out of the system, and the result will be water hammer.

When a section valve is opened and the water travels unrestricted in the empty lateral pipes, it creates a shock. The air in the pipe will be quickly voided through the heads, causing those abnormal velocities that damage pipes, heads and component parts. This is called dry line (or dry pipe) shock.

Protect your system with air release valves. Air release valves open to release air when the system is turned off, and close up when water runs through the pipes. Install these valves on the high points of the system, where air collects, so air can bleed out through the valves and not blow out through the heads.

Air release valves are among the variety of specialty valves that your local Ewing store offers. Ask about options from Jain, Landscape Products and Christy’s.

Watts offers this water hammer arrestor.

A water hammer arrestor from Watts.

Cushion the blow when water hammer does occur
You have another option when it comes to diminishing the harmful effects of water hammer. Go to your local Ewing store and ask about the water hammer arrestor from Watts.

You can swiftly and easily install a water hammer arrestor in new or existing systems using a standard pipe tee. This device incorporates a precharged, permanent sealed air pocket to absorb potential shocks. Its piston is the only moving part, and it can recharge the air pocket.

If you’re not cautious about how you turn on a system, then the possibility of water hammer will still exist—the change in velocity happens too quickly for any prevention to start in time—but you can neutralize the shock with an arrestor.

Don’t get hammered
The surge in water pressure occurs in a matter of milliseconds, so it’s always too late to stop it once it’s begun. But by using caution when turning on a system, you can avoid a water hammer event. And by installing a water hammer arrestor and air release valves, you can defuse water hammer’s damaging effects and avoid costly (and preventable) repairs.

Your local Ewing store can share more maintenance solutions with you. Stop by today to learn more about how you can better protect and maintain your irrigation systems.

How To Shield Irrigation Systems From Water Hammer graphic
David Olson
Find your nearest Ewing location at EwingIrrigation.com/locations.
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