I am having copper rerouted due to a slab leak. The plumber proposes tapping into the 3/4 running through the ceiling to one side of this two story house. This was done years ago due to another slab leak. I call that circuit 1. Now the circuit feeding the side of the house nearer the hot water tank, located in the adjacent garage, has a hot water leak. I call this circuit 2. The plumber's recommended fix is to abandon the 3/4 copper feeding circuit 2 with hot water (cut the pipe where it comes out of the slab on both ends and cap it), and feed that part of the house by tapping into the line feeding circuit 1 and connecting that line to feed the 1/2 inch feeding a sink. Is that a good idea? My thinking is backfeeding the this way will cut water pressure/volume to the rest of circuit 2. I would add that the cold 3/4" coming up into that side of the house is inside the perimeter wall and located about 15 feet from the hot 3/4 shown in center of picture 3. A pair of 1/2" pipes also emerge from the wall at the point where the cold 3/4 comes up. Picture one is of the 1" coming out of the slag that feeds the water heater tank, as well as circuit 1's abandoned hot and cold 3/4 . The other two pieces of 3/4 being the hot and cold for circuit 2. Picture 2 is where the plumber proposes to tap into the 1/2 inch. This is taken about 5 feet above the taps for the washing machine. When I look at that picture, it almost looks like the 1/2 comes off of 3/4, but I suppose it is wishful thinking. It is hard to see from a distance as a large cabinet is in the way. I will cut into the wall below for a better view, but assume it is all 1/2". [B](I got a better look and it is all 1/2")[/B] Picture 3 shows where the existing (probably leaking) 3/4 emerges from the slab below the laundry taps, along with for 1/2 inch. Two of the those four tap off of the other hot and cold pipes up a few feet up and in that wall. [ATTACH]78094[/ATTACH] [ATTACH]78095[/ATTACH] [ATTACH]78096[/ATTACH]

I am wondering if I can temporarily install a shut off valve to isolate a slab leak until I can work out a reasonable repair with a plumber and if so, can a compression fitting be used or must it be soldered? As is I have a hot water feed line that Tees off of the line going into the wall, down that wall, and beneath the slab. Said line was installed when another slab leak was discovered years ago. I would be placing the shut off valve between that line's "T" and where the second leaking line enters the wall.