Those metal studs didn't know what hit them.
You no longer have a vent for your toilet when you change the elevation
The back flow device needs to be tested and repaired. It is leaking there to let you know it needs service. In my state you would need to hire a...
Is the heater electric i presume since you did not mention any gas.
I think they are yanking yer chain. I believe all floor mount toilets have the same outlet to mate to a floor flange. The wax ring may have lost...
Its not code for IPC
What is the current psi in the house with nothing flowing
You would need to rework that tee that vents off to another fixture. How long is the pipe between the 90° and the tee.
Heat up the tee around the nipple.
You can also hang heavy plastic up to cover that wall
Is it just the kitchen. The hot side of the faucet may be getting over to the cold water side. I dont know what type of faucet you have.
It is either 1" or 3/4" or 1/2" pipe. To me it looks like 1" going into a 1" tee and reducing to 3/4" on the right. I am not sure if the branch is...
It is hard to answer without being there and seeing where the trouble spots are. If the water needs to come out the wall in a different spot, then...
It would just be a guess. I would have it flushed for sure.
You wont even have a fighting chance if you dont put some pictures up.
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