The water supply line is iffy and the shut-off valve on it is even more iffy, so I just shut off the main supply for the house.
The actual WC is a very small space -- it may originally have been a shower stall separate from the tub -- which means there's not a lot of room to work in. BF would have bitched 'til the cows come home, so I did it myself while he was still out socializing with all his little . . . . . . . . . . friends.
His contribution was turning the main valve back on, because he said "It's very sensitive."
Oh, spare me!