Landscape sprinkler-water hammer

[Kuma601]

When the system was first installed it ran well though now at about 17 years, I've noticed that when the 2 larger zones close it results in one hard water hammer smack. More so for zone #1 which has 12 heads on it. I've adjusted the head patterns down to lower GPM rates and adjusted the flow from the valve but cannot eliminate that hard closing impulse.

Thoughts on what I should be checking or replacing?

 

[nadogail]

Add an Air Cushion in your system to cushion the hammering, it can be as simple as capped pipe, full of air, that will absorb the shock from the closing valve. This asumes your water pressure is not terribly high.

 

[The Cobbler]

maybe the control valve

 

[Wheelingit]

Some of those for irrigation are slow close. If they fail to close slowly you will get hammer. I suspect a bad valve. Disconnect the power one by one from the valves as they are running. See which one is the culprit.

 

[Kuma601]

Thanks! That seems logical the valve is likely worn after all this time, will check into that. These are the brass Champion ones so fortunately there are rebuild kits for them.

 

[K'ledgeBldr]

Usually, the most common cause is air in the lines. Though you can't eliminate all possible infiltration of air, you can certainly reduce it at the beginning of every season. By opening (removing the sprayhead) the end sprinkler of each zone and letting it run for a matter of 15-20sec. you should clear air from the line(s).

The secondary cause is the zone valves- and how they operate. Better valves operate "slowly" when opening or closing. So there is a gradual withdrawal of pressure on the zone- eliminating the hammer-effect that is usually associated with a fast closing valve. And there are also different styles of valve "heads"/"stems" which can also effect the valve's performance.

"Hammer arrestors" (like Watts https://www.ewingirrigation.com/21105010-1-inch-water-hammer-arrestor ) are certainly a way of mitigating the hammer-effect. Installing them in the correct place is paramount. But, I would certainly exhaust the two most common problems before adding aresstors.