How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manfuactured and modular homes
What is the difference between PVC and ABS plumbing pipe?
Tuesday, August 28, 2018
The most obvious difference between them is that PVC (polyvinyl chloride) is white plastic and ABS (acrylonitrile butadiene styrene) is black plastic. Both are approved by the major national building codes for use as DWV (drain-waste-vent) pipe in the Schedule 40 rating. The plumber in the photo above is installing ABS under a sink.
Which is better? It depends on who you ask and where in the country you are located. We see mostly PVC used as DWV pipe in our North Central Florida region. But ABS may be a little easier to install because it does not require the application of primer before the cement at fittings and is more popular in other areas.
If you are doing a repair to existing ABS pipe and want to connect PVC to it, or vice versa, a special green-color solvent glue is required that is specifically made for connecting them. There is an all-purpose solvent glue that is rated for both, but might not be acceptable to the plumbing inspector in your jurisdiction, because they may want to see the green color of the excess glue at the pipe connection to know that you used the correct type solvent glue.
A rubber transition coupling (also called a “banded joint”) secured with stainless steel clamps used to be required, because the solvent glues to were only rated for either PVC or ABS, but not both. Here’s an example of what not to do, shown below, that we found under a kitchen sink at a recent home inspection, with evidence of leakage at the connection.
If you are doing a slip joint connection between PVC and ABS, like in the photo below, no special work is necessary as long as the slip fittings match their adjacent pipe composition.
While PVC pipe is fine for drain piping, it is not approved by the building codes for water supply (pressurized) pipe inside a home. It can only be used for the underground water service piping to home. Once the pipe comes inside the home, it has to be CPVC, copper, PEX or any other plumbing material rated for the use.
Also, see our blog posts Are plastic pipes (PVC, CPVC, and PEX) safe for drinking water? and How can I tell what type of plumbing pipe I have?
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