In the last couple of days I have noticed strange groaning noises coming from behind the walls every time I turn off a water faucet or when the toilet stops filling. What is the cause of this, and it is something that I need to get fixed?
I thought it might have something to do with the fact that we’re having a cold snap, and the water coming in to the house is colder than normal.
It sounds like water hammer.
It’s definitely something to get fixed. It can weaken pipe joints to the point that you get a leak in your walls. Get a plumber to look at it.
Since it just started I’d suspect your toilet’s fill valve is worn and causing a vibration just as it tries to close. You can verify this, the next time you hear the groaning, by removing the tank lid and manually lifting the float device. If this stops the noise, you’ve found the problem. It may be possible to repair the valve, but it’s usually easier to replace the whole device.