Since buying our home a year ago i’ve noticed a knocking (or hammering) sound coming from the pipes in the crawl space. It’s not the hammer sound you get when you turn off a faucet or washing machine but rather when water is running. I hear the hammering when someone is taking a shower, washing dishes even when the toilet flushes. A plumber told me there’s a loose washer in one of the valves. Is this an expensive problem? Also, I once had a Plumber come over to check out a rattling valve a top the water heater (in hindsight, I think it was meant to rattle since it had a little ball inside). He simply took it off and replaced it with a small piece of pipe. I can’t remember if I had the knocking sound in the pipes already but do you guys believe the two might be related? The house is over 50 years old and single story. Thank you for your patience.
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Replies
If you have a city water meter on your line, it is probably the water meter knocking.
If it has a steady knock when the water is running, that's usually the problem.
If you do have a meter, you might check with the neighbors to see if they have the same problem.
I believe we are assuming the noise is from the supply lines, right?
I have encountered noises from supply lines that were not secured well to the framing of the house. If they are tight you can install a rubber insulator that can often help.
I have also seen noises from the DWV lines as well. Especially if the lines under the sink or shower are a combination of steel and plastic. The two materials expand and contract at different rates when the warm water flows through them. that may what you are hearing. If so, the only remedy is to change over to the same materials, either steel or plastic.
Water meter will make a rhythmic click-click-click sound when the water is running.
As with heating ducts, when you heat a water pipe it expands in length. If not properly anchored, the pipe may make a creaking sound as the hot water begins to flow, due to this expansion and the pipe doing a slip/stop/slip/stop through its mounting points. (This can also happen with cold water pipes, but wouldn't be nearly as pronounced.)
You can have a valve that makes noise. This can be a regular kitchen or bath faucet with a loose part, or it may be something like a check valve or pressure reducing valve where the water enters the house/crawlspace.
You may have gremlins.
In any event, none of these sounds indicates anything serious. (If it's a bad valve it may fail eventually, but that might not be for years.) You only need to get it fixed if it annoys you.
bono,
Have your plumber install a "hammer arrester".
Chuck S.