A leaky shower valve is more than an annoyance. With every drop of water that spills down your drain, you're spending unnecessary money on your water bill, as well as watching the valve deteriorate further, leading to a replacement. You can usually fix the valve in less than an hour using the proper tools and materials. In fixing the valve you not only stop the annoying sound of leaking water, but you provide instant stoppage to the constant draining of your funds.
Turn off the water supply feeding the shower, and cover the shower drain with a rag to prevent falling debris from going down the drain.
Remove the handle from the shower valve. Use a screwdriver to remove the screw placed in the centre of the handle. Unscrew the handle screw by turning counterclockwise. Turning clockwise is likely to get you sprayed with any water remaining in the pipes. Pull the handle off after unscrewing.
Remove the escutcheon plate placed against the wall of your shower. The plate is the round metal cover over the shower valve that your handle was connected to. Remove the screws securing the plate in place, and gently pry the plate from the shower wall.
Replace the gasket on the rear of the plate with plumber's putty. Remove the old gasket from the plate. Take the putty, and roll it in your hands until you form a rope that's large enough to fill the gap in the back of the escutcheon plate where the gasket was located. Place the putty rope into the gap, covering the entire gap except for a one-inch area centred on the weeping hole in the bottom of the plate. The weeping hole is intended to drain any moisture that collects behind the plate. Place enough putty so that it slightly overfills the gap.
Access the stem assembly by removing the stem sleeve by wrapping it in cloth and turning it counterclockwise with a pair of pliers. Remove the stem nut revealed with the sleeve removal using a socket wrench.
Examine the washer and O-ring on the shower stem assembly. If either appears worn, replace them with parts of the same size.
Remove the shower stem assembly by returning the handle to the stem and turning it counterclockwise. Remove the screw at the bottom of the stem, turning it clockwise, and examine the washer. Replace the washer if worn.
Use a penlight to examine the inside of the body of the valve. Check for any signs of damage, such as uneven wearing of the surface or etched lines. If damaged, replace the stem using a shower valve repair kit compatible with your shower manufacturer. Install the kit according to the manufacturer's instructions. If the valve is undamaged, return it to place, and replace the stem nut and sleeve.
Place the escutcheon plate back onto the wall. The overflow of putty should form a layer around the edge of the plate and the wall. Screw the plate back into place.
Replace the handle onto the valve, securing it with the screw.
Turn on the water supply and check for leaks.