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Replacing Old Clay Basement Drain Piping

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Older houses often have clay drain piping installed beneath a concrete slab floor. These systems can go decades without problems, but when problems occur usually the best thing to do is to replace the old clay pipe.

Old Clay Drain Pipe Replacement
Old Clay Drain Pipes

Why Replace Clay Drain Pipes?

Root Infiltration

Clay pipe is usually found in sections ranging from 12 inches to a couple of feet and traditionally has had its sections joined with a grouting seal. While adequate for containing the drain pipe’s effluent, this type of seal can exude moisture that will attract tree roots. Once root infiltration occurs, a pipe can quickly block, requiring measures to deal with the damage and blockage. While tree root infiltration usually occurs outside the perimeter walls of a building, the problems that result can lead to a need to replace piping under the basement floor.

Another reason for root infiltration can be cracked pipes. Clay piping, while capable of lasting decades, is brittle and subject to cracking from frost, physical impact, and shifting soil.

Basement Redesign

Often, the impulse for replacing clay basement piping comes from renovation, redesign, or changes to basement plumbing fixtures. A new basement bathroom or laundry, for example, will initiate opening the basement drainage system and can lead to the replacement of existing clay piping.

What’s Involved in Replacing Old Clay Drain Pipes?

Assessment and Excavation

First, the scope of work needs to be determined. It’s often the case that the initial assessment of work involved underestimates the extent of the final job, but experts in this work have the tools and knowledge to get an accurate view of the job as early as possible.

Drain pipe inspection cameras will reveal the layout, condition, and potential blockages of basement drain piping before work begins.

The assessment will answer questions such as:

  • how much piping should be replaced?
  • should the job replace all the clay pipes between the stack at the rear and the cleanout at the front?
  • what problems need to be resolved?
  • where should the concrete slab (basement floor) be cut?
  • how will the new system be connected to sewer lines?

Once these questions and others are answered, it’s time to start removing the old piping.

Removing Old Clay Piping

First, the water is shut off to prevent unexpected flows. Then, start the actual physical work. The tools used to remove old clay piping are not elegant or sophisticated: usually, a concrete saw and sledgehammer are used to open the floor, and a shovel used to remove surrounding soil.

Once the old piping is exposed, removing the old piping is relatively simple.

Replacing With New Piping and Making Connections

Placing new pipe occurs once the old piping has all been removed to the extent needed. Bedding material is laid down, new sections of pipe are laid and connected, connections are established to drains, tie-ins, and vents, the cut is backfilled, and the floor slab is re-poured where it was opened.

Design Considerations

Designing the new system is really where plumbing expertise matters. While it’s a simple thing to break open a floor and remove old piping, what ultimately goes in afterward will make the difference between success and failure. Much has been learned about plumbing since older systems were installed, so it does not make sense to simply replace the old system with something similar. Remember also this is [designing for the future.

The new system will need to consider:

  • connection to the outside sewer
  • connection to riser piping
  • installation of cleanout points
  • installation of floor drains
  • possible installation of a backwater valve
  • possible installation of a sump well and pump
  • appropriate piping slope to maintain effect flow

As well as these considerations, the new system will need to use the correct materials (DWV (drain – waste – vent) pipe is typically ABS or PVC DWV-rated plastic pipe), and the right connection methods. The transition couplings at the stack and to the piping outside the foundation need to be appropriate: PVC pipe will sometimes need to be tied into clay pipe as well.

The Role of the Expert

Having an expert do this work makes sense, as, although the concepts are simple, the details are not. In addition to knowing the materials needed and the design considerations to follow, an expert plumber will ensure that the work meets building code compliance and will provide a system that will satisfy the scrutiny of a building inspection. It’s important to do it right the first time, as returning to fix mistakes is much more expensive.

A “do-it-yourself” job has risks beyond being unexpectedly expensive: a bad job can lead to flooding, improper drainage, smells from bad venting, code violations, and insurance denials. Using an expert such as Master Drain ensures the work is done right, quickly, and cost-effectively.

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