Re: changing old galvanized pipes
Posted by CEA on April 13, 2004 at 10:02:40:
In response to Re: changing old galvanized pipes
Assuming there are no fixtures on the stack above the bathroom, and no fixtures on the stack below the bathroom that are not separately vented, you can use the 3" stack as the drain and vent for the entire "bathroom group" (lav, tub and toilet). The 3" drain from the toilet and the 1-1/2" drain from the tub tie into the stack at the same level using a 3 x 3 x 3 x 1-1/2" side-inlet sanitary tee. The 1-1/2" drain from the lav ties into the stack a few feet higher using a 3 x 3 x 1-1/2" sanitary tee. In this setup the stack serves as a "wet vent" for the tub and toilet since it also vents the lav. If any of the fixture trap outlets aren't within the critical distance of the stack, you'll have to separately vent that fixture; distances vary with code, but < 42" for lav and tub and < 60" for toilet should be OK. This is the minimum setup--you can always separately vent each fixture if you want. The more venting the better.

The washer needs a 2" trap and drain. Its drain can tie into the 3" stack below the toilet, but it will require a separate 1-1/2" or larger vent, either through the roof or connecting to another through-roof vent (i.e. the vent stack itself) at least 6" above the sink rim.

This is complicated enough that I'd recommend you consult with a competent plumber or your local inspector before you start tearing up the room. There is more to venting than most people think. Also, codes vary so any advice you get here may not be applicable to your location, or you may have other options we don't know about.

You can rent a chain cutter ("snapper") that you clamp around the cast iron pipe which snaps it neatly at the point of the cut. The easiest way to join PVC to cast iron is to cut the iron pipe between hubs and connect it to the PVC with a "no hub" coupling (rubber sleeve with a steel band and two pipe clamps that tighten). Remember that cast iron is very heavy--support big runs of it before you cut or you may be remodeling more than the bathroom. Good luck.

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