Anyone know why a water heater would be making a knocking noise?
Metal expansion?
It is the water turning to steam Usually because there is a lot of sentiment in the bottom of the tank . It needs to be flushed regularly
It does sound like a lot of sediment in the bottom of the tank. Did it sound like popcorn popping or similar?
Thanks guys. Joe you’re everywhere today. Thanks for the input. Another question with the TPR valve of the same unit. The have the pipe inserted into the washer drain. I know they can’t do it like this because, even though it’s technically an air gap, it doesn’t drain by gravity and its not observable. Re routing could be a pain. Any thoughts?
Yeah kinda like popcorn since you mention it…
That’s wrong, even in Mexico.
The best part about being a home inspector is you don’t have to create the solution. 
Was the WH in a pan? If not, that’s wrong too. If so, put the TPR to the pan.
Yes there was a pan, no drain line for it though. just a pan
I’m thinking sediment also. Is that a hose or soft copper? Either way you can’t see it leaking so it’s not right. If it’s close to an outside wall it can be sent outside.
Knocking sound could be a defective dip tube within the heater.
Doesn’t that cause them to make a crying sound?:mrgreen:
I agree, sediment and scale in the tank will cause localized boiling, resulting in a thumping or rumbling sound, kind of like a coffee percolator.
Cute Real Cute … Thanks for the chuckle… Roy
To quote a plumber I know, that when it (the sediment) can’t be flushed out “It’s the sound of the clock ticking til a plumber is there to replace it”