Hissing noise in pipe(s) near kitchen-no water leak visible

[elefanlisa]

Last night I started hearing a hissing noise coming from the area between my kitchen sink, dishwasher and the wall the dishwasher backs against. There's no leak under the sink. No leak under the dishwasher. I turned the water supply off to the house and the hissing stops. I'm on a concrete slab. I turned off the water to the two toilets because one has a defective valve or something in the tank and sometimes sprays a little water. Once I turned them off and went out to the meter I stood for 10 minutes and watched. The little triangle didn't budge. The red "hour hand" didn't budge. I cut a hole in the drywall and by dumb luck I cut right where the drain pipe drops down and just to the right of where the copper water lines drop down. I can see the wood footer of the wall and I can see a bit of the concrete. No sign of water. There's no dampness on the floor or in the wall. The only sign of any issue is that hissing noise. I am no plumber. I'm a single 42 year old woman. I sure can't afford to have walls and floors and slab torn up. If I had a leak, wouldn't the meter move??

 

[Jackrae]

I once experienced the same problem which turned out to be a small hole in the underground feed line below my house floor (also concrete).

You may well have a leak in the feed pipe under the concrete slab. One way of proving that you do have a leak is to do a pressure test. For this you'll need a pressure gauge fitted to one of your taps (faucet in US jargon).

With nothing consuming water take a pressure reading, then close your mains feed valve. Providing the mains valve is not a self draining type, your water pressure should remain constant - if it quickly drops then you do indeed have a leak.

But what do I know, I ain't a plumber

 

[elefanlisa]

Didn't your water meter register motion to show water was coming out somewhere?

 

[joe-90]

Is it a gas leak?

 

[elefanlisa]

My house is all electric, so definitely not a gas leak.

When I do turn the water supply off into the house at the meter, the hissing stops. But even with the water on to the house, the meter isn't moving at all.

I checked the meter almost an hour ago and noted the position of the hour hand and triangle and the water supply is on to the house. In that hour, nothing on the meter moved.

 

[Jackrae]

Your flow-rate could be too low to register on the meter. One type of meter I've dismantled contained a small 'turbine" impeller which has some clearance between the wheel and the chamber so extremely small flows simply bypassed the impeller. Small leaks can make a lot of noise. In my case I didn't have a meter on my supply so nothing to measure.