[size=4]I have noticed the sound of water running in the pipes along my bathroom wall even when nothing is turned on. The noise stops when the shut off valve to the hot water heater is off (and when the main water line at the street is turned off). No inside or outside the house are on or leaking. No moisture noticeable anywhere. I have had two plumbers come out and still left without confirmation as to if I have a leak and if so how many gallons am I leeking over a specific period of time. [/size]

[size=4]At the suggestion of a plumber, I left the hot water valve to the hot water heater on, I turned off all faucets and also turned off the toilets at their shut off valves and then flushed to be sure the toilets aren't leaking. I then took the pictures below 8 hours apart. [/size]

[size=4]My water bill has not increased, my gas bill has considerably (usage for this month vs 12 months ago). Could this be something other than a leak? [/size]

 

So, your house consumed 10 gallons of water when everything when no water was being used in the house. While it may indicate a leak 16 gallons a day is probably not enough to be noticed on a water bill.

Did you hear the running water when you were doing this test? If so then I'd say it confirms you have a leak. Water may be running down inside the wall. Does your house have a crawl space?

You don't need to do your test for eight hours, though that's a pretty definitive test. The black triangle on your meter will spin quickly when water is being used and is should be visibly spinning over the course of a minute or so even with a slow leak.

Is your house heated by gas/ You did not say where you are located so it's difficult to comment on your gas usage other than much of the country has experienced record setting cold.

 

Is this a single dwelling? Any other high usage of gas consumption such as gas heaters, stoves, fireplaces?

How old is the HW tank? Have you ever flushed it?

Are all toilets in good working order? Put food dye in the tank and look for leakage in the bowl.