I have water hammer in my 2 story townehouse. I have shut water off and turned back on and if i only open the downstairs faucets i don't get any water hammer but when i open the upstairs faucet on the tub and sink is when iget water hammer on any faucet in the house. Any ideas? It is only on hot water side.

Turn the water to the house off. Open all faucets and flush all toilets. Close all faucets. Turn on water.
When turning on water to the house always open the valve a little slowly. Open a little and let pipes fill up, then open the rest of the way. If you open all at one time you can blow out faucet cartridges. Doesn't happen often but can happen.

After water has been restored open faucets and let any air in the pipes out.

PS: Drop the caps. All cap in internet correspondence is considered shouting.

Hello Rebel,

Follow Harold instructions and you will be OK, and please don't use the Caps, Thanks.

John

Are you sure we are talking about water hammer here? Water hammer is one or sometimes two loud bangs when you turn off a fast acting valve, such as a toilet or a single lever faucet.

Upon rereading your post, I suspect you may be talking about a different sound, more like a rat-a-tat-tat sound. That would be a vibrating washer in a valve some where.