What to Do About a Leaking Waste Pipe

leaking waste pipe

A leaking waste pipe can be a minor event or a significant cause of water damage, depending on where the leak occurs. The waste pipe is a larger diameter pipe into which smaller household drain pipes connect. Typically, the waste pipe receives drain water from the shower, tub, sinks, washing machine, and similar sources. A waste pipe does not convey water from the toilet.

Waste pipes are routed underneath the house— beneath the floor or through the crawl space or basement—and may have many drain connections along the route to the main household sewer line. Depending on local building codes, the waste pipe may be black ABS plastic specified for sewer piping, while the smaller drain pipes connecting to it from individual fixtures can be white PVC plastic.

How Will You Know There’s a Leak?

A leaking waste pipe can be hard to detect and trace. Wastewater flowing through the pipe isn’t under pressure, so leaks may be subtle rather than obvious. Visually inspecting the crawl space and basement may reveal evidence of dripping, such as wet spots or pools of water.  

Waste pipe leaks may continue unnoticed for a long time, damaging the adjacent wood structure and providing favorable conditions for mold growth.

Where Is the Leak?

Because of the difficult location beneath the house and the multiple connections to various drains, locating waste pipe leaks can be very difficult. This is typically a job for a qualified professional plumber—not a DIY project.

  • Leakage that appears to originates from the waste pipe may actually be coming from a joint in a drain pipe in the house above. Leaking water may run down the drain pipe and appear to drip from the waste pipe.
  • Leakage at joints in the waste pipe itself may be repaired by cutting out the affected section of pipe and gluing in a new section and joint.
  • Another possible leak location is the junction where the waste pipe connects to the house main sewer pipe. A coupling or bushing at that point may fail and begin leaking—another case that requires the services of a plumber.

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