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Pictured are pipes entering my slab in the wall behind my water heater. The wall has cellulose insulation in it, so I can't see, but my best guess is that there is a manifold in the wall there. The leaking pipe in question exits about 20 feet away, but is a half inch pipe, these are 3/4".

Should I be looking for a secondary manifold, or could there just be a reducer or tee in the slab? My stepdad taught me not to put fittings under concrete, but I can't say it's never been done. The house was custom built in 1983, so I have no experience with the conventions and code s of the time, being born in 85.

I want to simply cut and cap the leaking pipe before it enters the slab. It's just stubbed out on the other end.

My plan: Place a shark bite hose fitting on the end of the leaking pipe, run a house out the window. Turn on the water heater, and crack the valve and see which pipe heats up.

At that point, I will cut the water, cut that pipe, put a valve on it, shut the valve and turn on the water again. If any taps are missing hot water, I can run a new PEX drop to those fixtures.

  • Does the property have radiant floor heating? The leak is IN the concrete? Is piping sleeved or concrete to copper? Concrete is corrosive. It will, in time, eat the cooper, especially if heat/cool/heat/cool (expansion/contraction). Get a thermal camera and see where the leak is. You may have work on your hands. You can always separate the zones and test with compressed air what sections to pipe in question feeds.
    – noybman
    Oct 22, 2017 at 20:54
  • Thanks for the followup. No, the floor does not have radiant floor heating. The pipe is sleeved, and cracked about .25 inches below the level of the slab.
    – Jeff H.
    Mar 1, 2018 at 21:18

2 Answers 2


Ok, so I got this sorted eventually. I cut a hole in the wall to expose the manifold behind the water heater, found the line feeding my leaking pipe, cut and capped it. That resulted in stopping the leak but also cut the hot water supply to 2 bathrooms. I then followed the wall with the leak to its end and cut another exploratory hole in the area where it abutted the hallway wall, and found more copper exiting the slab. After some more fiddling, I discovered that the 3/4 copper coming out of the slab was feeding the bathrooms that were missing their hot supply, and that the 1/2 copper tee off of that line that dove back into the same hole was the pipe that led to the leaking section. I then reattached the pipe at the manifold behind the water heater, cut and capped the 1/2 inch pipe in the hallway wall, replaced the drywall and borrowed a carpet cleaner to extract as much water as possible from my brand new carpet.

So the answer ended up being that there were no fittings under the slab, the pipe was merely run under the hallway to the opposite wall where it poked out to a tee which was run under the slab down the wall.

Builders ought to have to file the complete plans with the city. Figuring out the plumbing and electrical runs in this place has been a nightmare. Thank you all for your insight. It was helpful.


This looks to be part of an hydronic heating system. This can be a difficult repair. I recommend you consult a pro who specializes in hydronic heating.

  • Thank you for the feedback. There isn't a hydronic heating system in this house. The water heater directly above my head as I was taking this picture provides hot water to the master bath, 2 guest bathrooms(1 upstairs), and a half bath.
    – Jeff H.
    Oct 22, 2017 at 13:55

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