Strange vibration

[Inspectorjoe]

Friday I did an inspection on a house that had been vacant for five years. The owner had inherited it from his parents. He grew up there. It's a 1950 ranch with a half inch copper service and interior piping.

We were in the basement when we suddenly heard a VERY loud noise caused by vibration. We ran upstairs and saw nothing. Went outside and saw nothing, but we could hear that it was originating in the house. We went back downstairs again and found nothing. I shut the power to the house off and the noise continued. I pinned the location to the area of the kitchen sink. I put my hand on a floor joist under the kitchen sink and felt a strong vibration. Going back upstairs, I moved the Moen single lever faucet handle from side to side and the noise stopped for a second or two then resumed. I ran some water and the noise stopped permanently.

The owner grew up in the house and had never heard it before. He'd been spending quire a bit of time in the house over the past month cleaning it out and had never heard it.

What could cause such a strong vibration with no water flowing?

[Mark P]

Really high water pressure?

[Inspectorjoe]

I don't check pressure, but the house was near the top of a hill, so it most likely wasn't unusually high. But I don't see how pressure would have an effect with no flow.

[John Kogel]

I have 1/2 copper pipe in my house and the water pressure from the street is too high, about 90 psi. I need to install a regulator, but I hate plumbing.

We have one faucet in the guest bath ensuite that gets a loud vibration going like what you described. It is only the hot side of the sink faucet that makes the noise, and only if you crack the valve slightly open.

Was water off for a while before the inspection? There must have been a flow through the faucet valve, equalizing the pressure. Where you testing the dishwasher? Flushing toilets? Worse than that would be a hidden leak.

[Inspectorjoe]

The water has been on for at least a month. There is no dishwasher and the only toilet I flushed up to that point was in the basement, very near the underside of the kitchen sink. I'm fairly sure I would have heard it if it continued running after refiling.

[Jim Katen]

. . . What could cause such a strong vibration with no water flowing?

If the water heater had been turned on for the inspection, perhaps the expansion of the heating water was squeaking from the hot side to the cold side in the cheezy Moen faucet.

[Inspectorjoe]

The gas water heater was operating before I got there, but I did fire a dead cold boiler. I wonder if the check valve was letting water expand back into the supply line. The old style expansion tank located between the floor joists was pretty much completely filled with water.

That certainly sounds plausible.