For possible shower and bathtub leaks, it is suggested to start the investigation in the drainage and checking the wall. Lift the drain rack and check if the drain on the floor is loose.
Sometimes the plumber’s putty, with which the underside of the top of the drain attaches to the shower tray (or tub), has been broken or loosened or broken over time. This filtration is common and can be repaired by using silicone sealant instead of plumber putty.
Loose drain pipe.
Please note that recent plumbing codes require that drains that cannot be accessed for repair must be welded together with solvent. Glue these with PVC or ABS cement (depending on the material of the pipe). To avoid leaks and repairs (not counting the cost of equipment such as telescopic chambers), ensure that the shower and bath accessories are secured under the floor.
If there are watermarks on the ceiling of the room below the bathroom or pools of water on the floor of the room, check the overflow in the bathtub (the silver lid with a small lever that is just below the bottom outlet of the bathtub) and also the edges of the wall tile, due to the fact that it usually happens that the water sneaks between the wall and the edge of the bath. Often just by filling the bathtub above the silver lid the water leaks behind the overflow shield will appear. This is because the rubber seal is missing or is misaligned requiring a slight adjustment (a simple solution).
Another common leak is that the tub drain is not sealing while diverting water to the drain pipe. Replacing the bath drain should solve the problem.
Check the sealing around the mixer plate and the stem of the wall. Look for open gaps in the finish and the screws holding the plate.
Make sure that the shower head and shower arm are tight. Make sure that the shower arm is properly tightened and there is no water leakage inside the wall. Sometimes the threads are cracked inside the wall and the shower head is loose and staggering.
Knowing when to call a plumber, and when you can cope with a bathroom drain on your own, will help your bathroom remodel develop smoothly.