New York recently approved the use of PVC as drain pipes.
PVC is considered very “not green”, mostly because it basically takes forever to decompose, so it sits around in landfills for hundreds of years. Or it gets burned and lets off all sorts of nasty chemicals. From a practical point it is also much noisier than cast iron, which means you can hear your upstairs neighbor’s toilet water gurgling down the tube.
But cast iron is not as great as people say. It takes tremendous resources to make it. A lot of it is recycled but that also consumes lots of energy. And really nasty chemicals are used to make cast iron, namely coke which is a coal byproduct that creates huge levels of pollution to make.
Studies have shown that cast iron isn’t much better than PVC…..go figure.
One argument for PVC is that it is cheaper, a lot cheaper, both in material cost and installation cost, which means you have more money for other green improvements…..
The only real green option is clay pipes. But that isn’t allowed except for deep underground sewage pipes where the surrounding earth lends the needed support to the clay. It would work for houses but probably not on a mass scale where everything needs to be tested, certified and to code.
So it is a tough call. In the green show house we’re building I’ll probably go with a mixture of PVC and cast iron. I’ll use cast iron where soundproofing is important, which is basically everywhere, and then PVC in the few places where it is not important.
Here is an interesting article on the subject from GreenBuilding.com. The cast rion/PVC part is toward the bottom.