[LazyPup]

When installing a DWV (drain, waste & vent) system we must select the appropriate materials from a list provided in the codes and all House sewers, Main drains, branch drains, waste arms, stacks and vents must be sized in accordance with a set of very exacting tables provided in the codes.

When one considers that a single family residential dwelling will typically require a 3" main drain, and futher understanding that a 4" line has nearly 8 times the DFU (drainage fixture unit) load value of a 3" line, it would then stand that it would be nearly impossible for a residential structure to require a line greater than 4".

In residential applications Cast Iron pipe is generally used in sizes ranging from 2" to 4". Occassionally we will find 1-1/4" & 1-1/2" cast iron pipe but that is rare.

While cast iron pipe is seldomly used in residential applications today, before the introduction of ABS or PVC plastics, cast iron was the norm.

Typically all lines of 2", 2-1/2", 3" and 4" were cast iron, while the 1-1/2" or 1-1/4" lines were made of galvanized iron pipe, copper pipe, brass pipe or lead pipe.

A water closet is required to be connected to a 3" or 4" line, therefore you will never find a closet flange attached to a galvanized iron pipe.

Occassionally we will find a flat brass closet flange attached to the end of a 4" lead closet bend, which was a lead pipe 90deg elbow made specifically for attaching the water closet. The use of lead piping is no longer permitted and when we encounter lead closet bends that need repair we are required to replace them with Cast Iron, PVC or ABS.

When copper or brass pipe is joined to a cast iron pipe system it is usually joined by means of a leaded joint in the same manner as a cast iron to cast iron joint.

When galvanized iron pipe was used to make the 1-1/4" or 1-1/2" branches or waste arms it was normally attached to the cast iron pipe by means of a sanitary tee that had an NPT (National Pipe Taper) threaded hub as the side opening. Pipe dope was applied to the galvanized pipe threads and the pipe was screwed directly into the cast iron hub. Occassionally we do find instances where the galvanized iron pipe was set directly into the cast iron pipe hub and leaded in place.

Depending upon the age and amount of rust on the cast iron and galvanized pipe it is occassionally possible to unscrew a galvanized to cast iron threaded joint but it is highly unlikely that a typical homeowner would have the means to do it. In my experience to unscrew a 1-1/2" galvanized iron pipe from a cast iron hub you will need a 48" or 60" pipe wrench. (at over $200 a copy not many homeowners have a 5ft long pipe wrench lying around their shop area.)

The easy solution is to cut the galvanized pipe off about 3" from the hub then join your new ABS or PVC by means of a rubber FERNCO coupling however in instances where the point of the leak is at the threaded end of the galvanized your only option is to either remove the galvanized or replace the cast iron tee.

Removing the galvanized pipe from the threaded cast hub or a leaded hub is at best a very tedious labor intensive job. You begin by cutting the galvanized about 1/2" to 3/4" from the face of the hub. You then use a heavy hammer and a chisel or drift punch to drive one wall of the galvanized pipe inwards. As the pipe wall folds in on itself it ultimately reduces the outside diameter of the galvanized to a point where you can pry it out.

Once the galvanized pipe is out, if you have a threaded hub you can clean the threads with a wire brush, then apply pipe dope to a PVC or ABS thread adapter and screw that in place to start your new run.

If it is a leaded joint, once you have started to colapse the galvanized pipe in on itself you can try to pry the lead out in the manner described above.