If it's a "manifold" style you should be able to isolate the bad circuit and reroute a new one.
Shut down Hot water to try and determine H or C.
Do you know if they put the pex in conduits or just poured into place?
The hoses are run in pvc conduits.
Problem is, the manifold doesn't seem to still work 100%. Some of the circuits, when the lever is thrown, it doesn't seem to completely shut the water off.
You have bad valves, there leaking internally,,,,,Old Gate valves?
I read threads like this and just cringe,,Get the pro’s on site ASAP….
Homeowners can be their own worst enemy……
Your about to make honorary mention in the 24 hour campfire Death match, House vs Water….
Hope the damage isn’t too extensive.
