How do you fix a urinal that after flushing the water runs down and out onto the floor?
I am assuming that you are talking about a wall hung urinal!
Most urinals have a mounting bracket where the urinal seals against
the drain line. There is a soft foam gasket that makes the seal
between the urinal and the drain line. First, secure the water to
the urinal, remove the flush valve, there are usually 2 screws or
bolts located on at the bottom of the urinal, unscrew these and
remove the urinal from the wall, replace the gasket and then
replace the urinal in the reverse of removing.