Dual Bath Vanity - Water Hammer Arrestors at each vanity or...?

[SomeOldGuy]

Title says it all.

Thank you.

 

[Reach4]

Water hammer occurs when you stop water quickly. Lavatory valves are hand controlled, so they seldom need water hammer arrestors.

 

[Sponsor]

 

[SomeOldGuy]

In this case, there is currently one there for cold and hot. I think the factor is that it is only about 10" from a manifold and the arrestor is there in the vent that there is sudden shut-off at some other point?

 

[Jadnashua]

It would be unusual that a vanity sink faucet would benefit from a hammer arrestor. Some toilet fill valves stop abruptly, things like washing machines, dishwashers, ice makers, and similar devices that have solenoid valves that close quickly can cause hammers. I've seen a few shower valves that specify their use, but they're in the minority. A hammer arrestor works best when it is connected as close as possible to the offending valve that is closing quickly. WHomever installed it there, may have been trying to quiet the toilet, and having one there would have been the better choice.

Those are probably not necessary. Each situation can be different, but needing one(s) there, would be unusual.