Ghost Knocking

19 years ago

Hey everyone.

My pipes are knocking but it's random and not when opening or closing a fixture.

I am under the impression that pipes only knock when the water is turned off quickly. This led me to assume that my toilet flap was leaky or something but that's simply not the case.

It's copper pipe, 1.5 bathrooms; laundry w/washtub; kitchen sink; and two outside spigots.

I am baffled as to what might be causing the knock. Could it be a leaky pipe? Could there be ghosts in my house?

Any ideas would be much appreciated.

Thanks!

Featured Answer

pinocchio

19 years ago

Certainly not, el Turtle. Hot water does not need to be heated. On the other hand, maybe itÂs the COLD water heater. I donÂt know. I think thereÂs information missing. Meanwhile I canÂt help thinking an extra set of knockers is not all bad.

And when that gets to be the issue, you can call Bust Go-sters. TheyÂre like that #2 rental outfit. They try harder. IsnÂt modesty a beautiful thing? Yah. I thrive on it.

Anyhow, getting back to the matter at hand, I donÂt believe ÂknockingÂ is the right word. When pipes creep within their hangers, they make a sound that might be called a knock or a clunk. That is, thermal expansion and contraction, depending on the heat being added or removed, makes the pipes creep and move and make a noise.

This change occurs when the system is otherwise at rest with respect to the movement of water. The noise can then occur when it is not expected, or as the OP called it, randomly.

Pinoke

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Comments (6)

kudzu9
19 years ago
Water hammer (knocking) is the term that is used for the noise you hear when faucet is suddenly turned off. However, heating systems, such as radiators, or radiant heat systems, etc., can cause knocking due to pipe expansion from the heated water. What kind of heating system do you have?
pinocchio
19 years ago
RE: Ghost Knocking:
Knock, knock.
WhoÂs there?
Boo.

A change in pressure can create a force that shows up as noise. Do you have a well, which operates in the background?

Pinoke
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lazypup
19 years ago
There is the remote possibility that you do have a ghost but since ghostbusting is outside my area of expertise for the moment let us consider all the plumbing possibilities.

First off, you are correct that the water closet flapper is the most common cause of irregular water hammer however a leaking flapper can be so subtle as to go totally unnoticed by visual inspection.

Begin by putting some food coloring in the water in the toilet tank then wait a half hour or so and see if the color is getting into the water in the bowl. If so, the flapper is leaking. (Many local hardware stores have a small two pack of dye pellets for this test that they will give you free).

If you don't have the food color or dye packs you have both a bathroom and a half-bath so you could turn the water off to one toilet and use the other for a day then reverse the process to see if it stops the water hammer.

Once you have ruled out the toilets there are other quick acting valves in the house that often go totally unnoticed.

It could be a refrigerator ice maker supply valve, dishwasher fill valve, washing machine fill valve, a makeup water fill valve or a lawn irrigation control valve. Code now requires that all of these valves must have a water hammer arrestor in the near proximity of the valve.

For the record, you can rule out a leak because water hammer occurs when the flow is rapidly stopped, but a leak would remain constant so it will not produce water hammer.
lthurtle
Original Author
19 years ago
Thanks people. As always, Lazypup, you are a wealth of great information.

I am on city water, have forced air heat, no ice maker in fridge, no irrigation system, and the knock happens irregardless of D/W;W/M use. I'm going to have to try the dye in the toilets.

I'll let you know what happens ... otherwise "Who I'm gonna call? Ghostbusters!"
lthurtle
Original Author
19 years ago
Well it's not the toilets :(

could it be the hot water heater?