Shock Absorber (aka Water Hammer Arrester) 1

[MinnesotaSlinger]

My company doesn't have ASSE 1010, the ASSE standard relating to water hammer arresters. Anyway, I was wondering if either in ASSE 1010 or through some other standard there was a way to know when a water hammer arrester must be installed in a domestic water line. PDI WH-201, which I have and which I've read, has a lot to say about how to size them and when you need to have two in a branch instead of one (that is, when the branch is longer than 20 feet), but it seems sort of vague as to how many fixtures (e.g., water closets or sinks) one must have before a water hammer arrester is required.

Would you really need a water hammer arrester if you had only one or two fixtures in a branch? When do you specify water hammer arresters and when do you leave them out? Do you add them in even if you have just one sink or one toilet?

Thanks.

 

[PEDARRIN2]

Water hammers should be used on piping that has quick closing valves like solenoid valves or flush valves. Water hammer arrestors should also be used if you have higher pressures or velocities in your domestic water piping - or if you have a booster pump in operation.

Common installation of plumbing piping in a chase is use of decreasing sized piping as the fixture units decrease (like 2"->1.5"->1"->0.5" as you go from water closet to lavatories. As you decreas in size, the velocity will go up. If this water is stopped suddenly, you get a pressure wave and water hammer happens.

I typically use a full size manifold pipe in the chase - whatever size I brought into the chase. Then each fixture ties into that pipe. This decreases the chance for the higher velocities and the pressure wave.

If you only have one or two fixtures - like a single toilet room, you could probably get away with no water hammer arrestor. But I would put it in anyway, just to be safe.

 

[bimr]

Check out the

http://www.siouxchief.com

website for a discussion of the effects of water hammer.