How to Avoid Water Hammer in Sprinkler Pipe?

6/11/2020

Please can someone give some information regarding the filling speed of a empty pipeline to a sprinkler line?

In my case there was water hammer in a 6” line, The 16” firewater line was under 175 psi pressure and the opening time was 9 seconds.

Is 3 feet per second more realistic? Or is there a NFPA standard that addresses this? Thanks in advance for your support!

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5 Comments

FIREPE25

6/11/2020 10:22:29 am

My understanding of water hammer is that it is more of a problem associated with when valves are shut and water stops flowing abruptly. That is why NFPA 13 requires slow close valves. It is also why fire hydrants are closed very slowly to ensure the underground pipe is not damage.

Jose BOHORQUEZ

6/11/2020 12:20:34 pm

Es correcto la informacion , para complementar el golpe de ariete también de produce por la micrexplosiones que se dan al activarse las unidades de bombeo.

MIGUEL ANGEL D ADARIO

6/11/2020 11:21:38 am

In my experience, it would be advisable to make the pipe very slow and complete, releasing as much air as possible at the opposite end, mainly from the highest points. Once this is done, it must be pressurized, (for example, by means of the jockey pump).

Jeremy James

6/12/2020 08:16:49 am

Contractor: Is this on a dry system? Either way, cracking the valve and letting the system fill slowly for a few minutes will decrease the hammer. We typically use earthquake bracing, required or not, throughout the feed main piping, where we have a 90 and turn directions.

Bruce Verhei

6/15/2020 04:09:59 pm

Are you concerned with the water system outside your building or only your system?

My water departments were concerned about rapidly opening valves too, meaning not happy at all.

They know that FF’s open hydrants as fast as possible at fires, and some even know about dry system trips, vaguely.

They said it can cause problems in their systems.

If you are taking water from a municipal system that has additional pumps that kick on at high flows, or your at a lower elevation pressure zone, fed from a higher pressure zone, that has valves that open to provide more water during a large fire, filling faster can have implications well beyond your project.

Do this a 5pm, and some water tech has to come back in to check valve in a pit, or a pump at a station just because you think it’s funny? Ever wonder where weird rules about all tests shall be done prior to noon etc come from? Funny, huh?

Rule of thumb: Cause the least rapid pressure/flow changes you can.

Best.

Bruce Verhei

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