new home knocking pipe

Hello,

We just moved into a 2yr old home and we have encountered a situation.

In the kitchen when we run hot water we hear a knocking sound almost like someone is on the other side of the wall knocking. Even after we turn off the hot water the knocking continues for another 30 to 45 seconds.

I have read other postings about water hammering but no one ever mentions that it continues to knock after they shut off the water (like in my case).

It doesnt happen anywhere else in the home only in the kitchen.

And im not sure if its the hot water pipe or the drain that is causing the knocking. From what I can tell the knocking is close to the faucet height of the wall.

One more thing I would like to add, is this something that can become serious in the long run? Will the knocking cause any type of damage or leaks in the future?

Thanks...

This is a common situation with PVC drain pipes. This kind of plastic expands and contracts a fair amount with temperature changes. If the pipe is rubbing against anything, it will make "ticking" sounds as it expands and contracts. If you can isolate it and make sure it doesn't rub any more, most of the sound will go away. It won't hurt anything except your peace of mind.

As hot water flows into a pipe, the pipe expands. The expansion rate is different for different kinds of pipe, and is pretty impressive for some (e.g.) CPVC. As it expands, it moves relative to the house framing, and a knocking sound often results as the pipe lurches back and forth. After the walls are closed in, it's pretty tough to fix.

Is it a serious problem? Could be. Or not. Should it have been disclosed at sale? Dunno. Would I try to fix it? Well, I recently had to re-plumb my house and I now have the same problem with my kitchen supply pipes, both H and C. The area where the noise is generated is readily accessible. I'm not going to do anything about it. OTOH, I can envision situations where the problem could lead to long-term failure of the system. How long are you planning on staying in the house?

Seriously, I'd probably try to have a look at the area involved just to see if there's a risk of the pipe failing, or if it's just a nuisance. Odds are heavily in favor of it being a nuisance, IMHNPO. It can be easily fixed if it bothers you, once the pipes are exposed.

Thank you for the replies. I will do a little more research and see what would be my best results. if its just a bothersome noise i may just try to live with it. im not to handy when it comes to plumbing, electrical yes but not plumbing lol. In either case I thank you all for your replies.