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The drainpipe in our sink broke (corroded right through in several places). Not having the time to find my pipe wrench (much less actually replace the pipe) we called a plumber. The plumber replaced the drainpipe with PVC (under the theory it would be immune from corrosion).

So I got to wondering: Is there any reason to prefer one kind of drainpipe to another? I know that for blackwater lines you need to make sure the urine won't corrode the pipe, but for a kitchen sink does it matter at all? I could even use lead pipes since that water will be treated before anyone drinks it, right?

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Lead would be virtually impossible to find these days. PVC is standard and chemical-resistant (dishwashers are harsh.) Cast iron (usually without the old-fashioned joints) is sometimes used for sound-reduction .vs. PVC, more on stacks than individual drainpipes. –  Ecnerwal Aug 9 at 0:13

2 Answers 2

I think new sink drainpipes are almost all PVC. I recently replaced a corroded metal kitchen sink pipe with PVC, but in the store I noticed that metal downpipes are still available.

In theory PVC should be more resistant to chemicals and rust while metal is more resistant to heat. But most drain cleaners don't contain lye any more and nobody in their right mind dumps 500F fluid into a sink. Rust, however, is still a problem.

Yes, I think the concern with lead is the contamination of incoming water more than outgoing. And plumbers sometimes still do use molten lead to repair old drain tile junctions. But I doubt most municipal water treatment facilities are equipped to extract a high level of heavy metals, so it's probably better to get the lead out anywhere possible.

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There are two main factors that determine what is used:

  1. Code requirements (as well as the project's specifications)
  2. Cost

ABS and PVC are the cheapest, however there can be limitations with their use in larger buildings due to fire code requirements.

Where fire codes requirements limit the use of plastics, either cast-iron or DWV copper is used for the piping above ground switching to either Chrome or Brass p-traps for the sinks. However depending on the authority having jurisdiction (usually the local inspector), PVC or ABS p-traps may be permitted within the sink cabinet.

XFR-PVC does meet flame and smoke spread requirements and depending on the project may be allowed to be used instead of Cast-iron or DWV copper.

Chrome is also used for wall hung sinks where the p-trap will be left exposed.

Labs that use chemicals and acids typically use either glass or special acid resistant plastic pipe and p-traps.

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