Replacing a shower base is a difficult and time consuming job. Fortunately, it is not something that you need to do very often. The only reason that you will need to replace a shower base is if it is leaking. Generally, it is not possible to repair a shower base, necessitating a complete replacement of the unit.
Also consider replacing the entire shower cubicle at the same time, since you are going to have to remove all of it to access the shower pan. There is also a lot of other work involved as well, such as laying the new tiling or repairing any surrounding flooring or wall.
Step 1 - Make Necessary Preparations
Ensure that the water supply is turned off to the bathroom. To minimize risk, turn off the main water supply to the entire building before you start. Clear the area so that you can easily access the shower.
Step 2 - Remove Old Shower Pan
Removing the old shower base is half the job. Sometimes it can be more complicated than other installations, depending on the material of your shower base. Remove the shower doors which you should be able to slide and lift out of place. Then remove the rest of the shower cubicle from the wall. It will probably be attached by screws. Remove these parts until all you have left is the shower base itself.
Step 3 - Install New Shower Pan
Place the new base over the shower drain pipe. Ensure that the floor is level beforehand. Since you are replacing an old shower, it should already be completely level. When you have the base in place, attach it to the walls as directed by the manufacturer. The method you use will depend on the material of the shower base.
A shower base kit will likely come with preset screw holes and screws allowing you to attach it in place easily. In other cases, you may be installing the shower base using a special mortar mix as directed by the manufacturer. Fasten the flange to the wall, making sure that the base flange is attached to the studs.
Step 4 - Install Drain
The drain should fit into the pipe at the center of the base. Ensure that the rubber washer is flat against the nut before you fasten them together. Doing so will ensure that there is no leakage. Screw the drain cover into the pan.
Step 5 - Apply Sealant
Once the new shower pan has been properly fixed into place, apply silicone sealant to the edges. Leave the sealant to dry for at least 24 hours before using the shower.