Pipes hissing, goes away when WH supply is off

[Spoolofpipe]

Gents

need some advice

Yesterday I went to use the facilities in the middle of the night and I heard a hissing noise (generally I can barely hear myself think with my wife and daughters haha jk)

I lumbered around and couldnt find a louder spot, I thought it might just be my sprinklers which run in the middle of the night on certain days

Today I went around and I can hear the hissing in the half bath down stairs, the full bath which is above the half bath, and in the washing machine and dryer room (its more like a closet)

So I shut off all the supply valves to all the fixtures in the house including my sprinkler system, still hissing
I went into the garage and shut off the Water heater supply valve and BINGO, no more hissing

so that makes me rule out any running toilets

I had problems with the valve to the girls shower leaking through the seat and replaced it about 2 years ago, since its one of the hissing locations I pulled the cover and checked the valve body and its dry

Since I am just a lowly engineer, do you guys have any tips to find the leak?

I am thinking of just cutting the drywall under the washing machine box and checking for leaks

Thanks for any help!

 

[James Henry]

Check your temperature/pressure relief valve.

 

[Sponsor]

 

[Spoolofpipe]

Check your temperature/pressure relief valve.

Thanks for the idea, but no such luck

Went to the garage last night to look for more leaks, found a puddle by the wet wall

Cut away the dry wall, felt around, no leaks/moisture

Look down between my feet, and there is a little crack in the slab and water ever so slightly coming out....

Think I can flex seal it? (Joke)

 

[Michael Young]

sounds like you have a slab leak. is it all slab or can you get under the house and put you hands on that pipe?

 

[Reach4]

If I had access to a FLIR camera, I might see if I could see the hot water flow.

Is there a reason for you having a hot water line to be going under the garage slab, such as the WH being in the garage?

 

[Spoolofpipe]

sounds like you have a slab leak. is it all slab or can you get under the house and put you hands on that pipe?

no unfortunately its all slab, which I had a basement, I called out a plumber since I was a bit over my head on this one, he cut the line that was leaking where it goes into the slab, routed it in the garage ceiling over to the manifold with PEX

kinda wondering if I should have done it myself, my wallet is hurting a lot haha

If I had access to a FLIR camera, I might see if I could see the hot water flow.

Is there a reason for you having a hot water line to be going under the garage slab, such as the WH being in the garage?

No I have no idea why they put it under the garage slab when they built the house, its so stupid

the kitchen is right under the master bath, they could have easily used the wall right behind the WH as the main wet wall

only other hot water needs are the half bath and my kids bathroom, but those are also in the same location, could have been hit by a single run and branched off

 

[Tuttles Revenge]

We run pipe in the slab because its Cheap to install..
Any chance its thermal expansion opening a toilet fill valve thats out of adjustment?

 

[Spoolofpipe]

We run pipe in the slab because its Cheap to install..
Any chance its thermal expansion opening a toilet fill valve thats out of adjustment?

cheap in the short term

No, checked all the toilets, its definitely the run going under the garage slab, wouldnt hold pressure when he checked that run

 

[Jadnashua]

The hot line is often the first to go. If you have other pipes running under the slab, you might want to budget to abandon all of them and run the new stuff entirely above grade. How long they'll last under there depends somewhat on the temperature, the soil chemistry, and what gauge pipe was used.

 

[WorthFlorida]

In the southern states like TX and FL, all homes are built on concrete slabs and all of them have the pipes under the slab. My last home built in 1990 had all copper pipes and one neighbor did have a hot water line leak when the home was about 5 years old. My current home built in 2007 is all CPVC under the slab. A friend of mine had his single floor home built around 1987 had pipes above in the attic space. The problem is the cold water (maybe 75 degrees anyway) was always hot picking up heat from the attic. Under the slab allows straight runs between fixtures. There is a new development being built up the road from me and I haven't checked them out. With PEX used almost exclusively, not sure if they are run under the slab but I'l check it out in a few weeks and let you all know.