Should I kill the water at the main?
If you can’t isolate it at the fixture, yes — use the main, but only if you can reach and operate it without risk.
Why does this drain keep coming back?
A drain that clogs again and again is usually telling you something beyond the trap — check the branch, the vent, and the slope.
Tank versus tankless — how do I decide?
It comes down to how much hot water the house actually pulls at once, what fuel and vent path already exist, and whether the panel has room to spare.
Does old pipe automatically mean full replacement?
Not always — material, current pressure, leak history, and how hard the area is to reach all factor into whether it’s a patch or a full repipe.
Who’s checking the provider’s license?
That’s on the homeowner — confirm credentials, insurance, permits, and warranty terms before anyone starts work.