Installing your own back flush toilet can be a big, messy job. The toilet is heavy, the space is cramped, and if you're not careful, there is a high probably that you will wind up ankle deep in leaking water. Avoid these hazards be following the few simple steps below.
Step 1 - Empty the Water From the Old Toilet
First, shut off the inlet valve by turning the shutoff valve clockwise until it becomes tight and no more water is feeding into the toilet. Flush the toilet to remove as much water from the bowl and from the reserve tank as possible. You'll probably have to flush it more than once.
The next step deals with removing the old toilet. Be careful when lifting it, as it will likely still have some water left in it.
Step 2 - Remove the Old Toilet
Now, unscrew the water inlet line at the toilet, turning it counter clockwise. This can usually be done by hand. Detach the drainage pipe from the wall by turning the PVC lock nut counter clockwise. Unfasten the toilet from the mounting bracket at the bottom of the toilet using an adjustable wrench. Use caution when moving the toilet, as there will probably still be some water in it.
Step 3 - Place the New Toilet
Place the new toilet on the mounting bracket, but don't fasten it down yet. First, measure the distance between the toilet drain and the drain mounted in the wall. Now, you can attach the drain pipes. Use a saw to cut the 2½-inch PVC pipe to go from the toilet drain to the wall drain. Be sure that any excess you trim does not come from the threaded side. The smooth cut side should fit into the toilet drain and rest snugly against the wall drain.
Remove the toilet from the mounting bracket to install the pipe. Generously apply PVC primer to the outside of the pipe and the inside of the toilet drain. When the primer is dry (this should only take a few minutes) apply the PVC cement in the same fashion. While the cement is still wet, insert the pipe into the toilet drain and let it dry.
Step 4 - Secure the New Toilet
Replace the toilet on the mounting bracket and attach the wall drain to the toilet drain by turning it clockwise. This should be done by hand, but make sure you get it as tight as possible. Using a pipe wrench, attach the water supply line by screwing it clockwise. Use an adjustable wrench to fasten the toilet to the mounting bracket. Now, turn the water inlet supply back on by turning the shutoff valve clockwise until sufficient water pressure has built up.
That's all there is to it. Now you can stretch out and congratulate yourself on a job well done.