We have a hot water leak under the slab, Leak Detection Co. came out and said it is here. Popped up 1 tile poked through 5 inch slab. Found the pipe but could not get to leak. I tried following the pipe for 2 ft. but the slab went from 5 inches to 24 inches and the pipe is in the concrete. The area is right were hot and cold comes out of the ground. Cut one of the 3/4 inch pipes (hot) and capped. Figured out it is the pipe running to master bath. I want to use Pex tubing in attic over to master bath. Where does the 3/4 inch pipe usually come out of ground in Master Bath. Would it be in the middle of the shower and tub area. The leak detection co. marked a spot and said the pipes are here, I popped a hole outside in the stucco and they were hot and cold pipes coming out of the ground but they are 1/2 inch not 3/4

Hi FTP

Unfortunately, there is simply no standard place where pipes come out of a slab in a bathroom. In many slab jobs, there is a central location the pipes come out of the ground (under a vanity, in a closet, behind the shower at the shower valve, etc.) and then they run pipes to each fixture from that central spot as you suspect.

If you isolate these 1/2" pipes from the slab piping and feed air into them it may be that you will be able to tell exactly which fixtures get supplied by the pipes...maybe? If you are lucky, these 1/2" pipes feed entire bathroom...

Back to you..

Mark

As Mark stated above, there is no set system to such installations. Every plumber does it his way.

Years back, when we used to install soft copper under slab, we ran 3/4" pipe from bathroom to bathroom, in loops, and always ended up behind a tub or shower. From there we distributed 1/2" lines to individual fixtures in that bathroom. But that was our way of running pipes.

It really takes an experienced plumber to trace it the way so you don't end up with too much floor / wall damage. People who trace pipes are not necessarily "it". See if you can get an old plumber over to help you with it.

Milo

Also rememeber if you are replacing with PEX the inside diameter is about a quarter less than copper pipe. So a 3/4 inch PEX pipe is roughly 5/8'' copper tube size.