Banging Pipes only at night

[Adam81]

So, every night for the past 2 weeks or so in our basement there is a banging sounds that happens in the wall (sounds just like the pipe "banging" or "hammering" we all know) and starts around 9pm at night and lasts all night. From what I can tell it stops in the morning sometime. I have stood down there for 5 minutes during the day and can't hear a thing, but at night I've been down there for hours at a time and it doesn't stop.

Does this make any sense?? It's almost a rhythmic hammering sound, 99.7% sure it's a pipe of some sort. I checked our water pressure and it's right around 54psi, where the pressure reducer is set to on the main line coming in the house.

The sound happens right under the master bathroom on the main floor. I've done the flapper valve test (food coloring in the tank) and don't show any leaks with that method. I'm really at my wits end here.

Thanks in advance.

 

[Adam81]

It's already started tonight, just went to listen (6:08 pm).

I've had critters in the walls before and it's def not that, this sounds like a pulsating pipe of some kind....mechanical sound....hard to describe. Sounds like a pipe in the winter when it expands and you hear it in the wall, but it's doing it every 10-15 seconds.

Thanks

 

[Matt30]

Do you have a water conditioning system?

 

[Adam81]

No we don't have a water conditioning system.

I did take a video of it so you guys could hear the noise.
Never any rustling, scratching, etc....just this banging noise every few seconds.

[ame]http://www.youtube.com/watch?v=WC1Xr9q7GQ0[/ame]

 

[IFIXH20]

Just throwing this out - What about house settling. My home makes lots of noise after sunset.

 

[Sweeney-Renewables]

You could have air in the system. Try bleeding the system at the pump out/inlet.