How to Replace Old Drainpipes Under Basement Floors

Break up the concrete slab above the drainpipe with a jackhammer and remove the concrete pieces. Wear adequate eye, ear, hand, lung and foot protection when operating the jackhammer. Leave the edge of the broken area jagged for better adherence when the concrete patch is placed later. Avoid damaging the footing for the wall, which should be left intact to support the wall. Cart the concrete pieces off from the work area.

Remove the old drainpipe and any other materials in the trench, including gravel and filter fabric. If the gravel is being reused rather than replaced, it should be thoroughly rinsed to remove any sediment. Make sure that the trench shape is restored so that it is at least 6 inches deep and wide.

Line the trench with filter fabric.

Place an inch or two of clean, coarse gravel in the trench. Bear in mind that, when building up the bottom of the trench and laying pipe, the drainpipe must connect to the existing pipe, an inlet on the sump pit or extend to an outlet and the pipe must maintain a slight slope toward the sump pit or outlet.

Cut a section of suitable drainpipe or tiling to replace the old pipe. Perforated PVC or plastic piping is typically used for this application and can be cut with a hacksaw.

Test-fit the pipe and any hubs or couplings together without adhesive. Consider marking the way the pipe and hubs fit together or the spot on the pipe that indicates how far into the hub it should penetrate.

Join the sections of new pipe together and to the old pipe or sump inlet as needed. Use a glue or contact cement suitable for use with the specific pipe material. Some pipes or sump baskets may have threads for couplings, but generally glue must be applied to the pipe end and fitting hub then the pieces joined together quickly.

Check to make sure that the pipe slopes toward the sump system or outlet and make any adjustments, as needed, before continuing.

Fill in the space on either side of the pipe with clean, coarse gravel.

Cover the gravel and pipe with filter fabric. Add enough gravel in the trench to build it up so that only enough space to accommodate the thickness of the concrete patch remains.

Lay concrete patch in the area where the concrete was broken up and removed. Prepare the patch, according to the manufacturer's instructions, pack it into the space with a trowel and smooth the top with a straightedge.