Joining PVC to Cast Iron Question

[Tom Nicelley]

I needed to replace a damaged section of 4" PVC (and add a proper drain for our washing machine). It seemed to be a no-brainer, the existing PVC attached to cast-iron near the floor. But when I removed the old connectors, I discovered that the "stub" of cast iron was corroded and cracked, and now leaks. This "stub" is only 5" long and leads into a cast-iron wye that comes up through the concrete floor. Obviously, the cracked "stub" needs to come out, but then how do I connect into the wye? And what would be the best way to remove this "stub" without damaging the wye? thanks

[LazyPup]

Fortunately the stub is open so you can get to the inside of the WYE. Get a large bundle of rags and tie a heavy twine or wire around them, then jam the rags down into the WYE below the stub. The rags will catch any shards of the cast stub as you break it out and you can later pull the rags out with the twine.

The easiest way to remove the stub is break it out. Cast iron is very brittle so breaking it is relatively simple. Hold a large (2lb) hammer against the outside wall of the stub on one side and hit the wall on the other side with a second hammer. The cast iron will crack and break away. Once it is broken you simply pull all the pieces out.

You will see the lead ring on the inside of the hub that was used to seal the two sections of cast iron. Drill a 2 or 3 1/4 or 3/8" holes down through the lead close together to get a starting point. You can then insert a pry tool into the holes and pry the lead away from the inside of the cast hub. ( an old automotive tire iron makes a perfect tool for prying the lead out.)

Using a flat screwdriver you can then pry the old oakum out. (Oakum is a fiborous material that looks like a piece of frayed rope.)

Once you have all the old cast iron, lead and oakum out you can now pull the twine and remove the ball of rags.

You can now set your new PVC into the hub and pack some Oakum around the outside of the PVC and the inside of the hub until the Oakum is about 1/2 the depth of the hub.

You can then fill the remainder of the hub with plastic lead or Plumbers epoxy. ( I prefer to use a product called "Black Swan Iron paste" which is a liquid plastic lead sealing compound in a paste form and certified for use on cast iron, steam and gas lines.)

If you cant find the liquid lead you can use Plumbers Putty, epoxy. It is a two part epoxy putty that has a light grey outer part and a dark grey core. You knead the two parts together until is it a consistant color to activate the epoxy, then press it into the joint and form it.

On the top end you should have the small diameter end of the cast (spigot end). You can couple the PVC to the spigot end of the cast with a 4" PVC X CI (CI= Cast Iron) rubber Fernco coupling.

[HayZee518]

Tom here's a diagram of what lazypup's talking about

http://www.homerepairforum.com/images/uploads/2004-12-15_drain2_w550.JPG

[LazyPup]

Check the illustration forum,,i have prepared illustrations for breaking out a section of cast iron pipe & joining cast iron to PVC or ABS

[Tom Nicelley]

Thanks for the help guys. Also thanks for steering me to the illustrations forum-I hadn't seen that before.

[LazyPup]

The illustration forum is a new feature that Troy installed about two or three weeks ago. We have been working on creating some illustrations that will help answer the questions...