How to Fit a Toilet Waste Pipe

Updated November 21, 2016

When replacing your old toilet or setting in a new one, be sure that the pipes correctly fit to avoid leaks and possible water damage. The waste pipe is the area the water drains from after use, and must be disposed of without leaking onto sanitary surfaces. The pipe connects to the base of the toilet through a snug fitting known as the wax ring. This ring will give the toilet the seal it needs, but without the right pipe, even the wax ring cannot prevent water damage.

Measure the waste pipe and determine whether it is the same size or larger than the toilet drain. Choose one of two rings -- either the wax ring is larger than the rubber connector that slides into the waste pipe, or it is the same size as the rubber connector that slides into the waste pipe.

Purchase the wax ring suited for your job. If your toilet drain is the same size as your waste pipe, as is the case with most toilets, the first option is the right choice. If your toilet drain is larger than the waste pipe, choose the second option.

Set the ring onto the base of the toilet while it is empty and upside down. Press it firmly and then set the toilet onto the waste pipe and push the rubber connector into place.


If your toilet drain is smaller than the waste pipe, you run the risk of leakage. The best solution is to add a fitting to the end of the waste pipe beneath the floor, via the basement, to reduce the width of the pipe. Most homes are done this way, but older homes and businesses may have fittings that are out of date for newer toilet designs. If the necessary adjustments are not made, water can leak because the wax ring cannot seal the large area, weakening and softening the floor under the toilet.

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