Concrete Foundation Toilet Plumbing

Attach an extender pipe to the home drain pipe so the piping extends above the concrete once the concrete is poured and dried. The size of the extender pipe must match the size of the existing drain pipe. Pour the concrete and let the extender pipe set as it dries. After it dries, cut the extender pipe portion flush with the floor. Since the concrete will serve as a foundation for the toilet to sit on, make sure the dried result forms a level surface.

Fit the toilet flange piece on top of the extender drain pipe. Flange sizes correspond with standard drain pipe sizes, which come in 3-inch or 4-inch diameters. Insert the bolts that come with the flange kit into the slots around the flange lip. Apply a glue or solvent adhesive to secure the flange piece to the drain pipe. Flange fittings can be made of metal or plastic, so use the type of adhesive best suited for the the flange material.

Install flange spacing if a concrete foundation dries to a lower level than expected. When this happens, the concrete sits lower than the flange piece can reach. Place the flange fitting onto the drain pipe, and set the spacer piece on top of the flange. Use a silicone caulk or solvent adhesive to secure the spacer to the drain pipe. Once it is dry, secure the spacer to the floor by inserting bolts into the slot openings on the spacer

Set the toilet onto the flange and drain pipe fittings so the toilet pipe, flange and drain pipe line up evenly. The toilet should sit level and should be securely in place. If the concrete foundation is uneven, the toilet will lean, tilt or rock when in use. This condition can cause significant damage to the home’s drain pipe and cause the flange and spacer fittings to loosen over time. If the toilet pipe does not line up with the drain pipe, the drain pipe may have tilted as the concrete dried.