cast to PVC

[Limp Arbor]

I need to add a trap to my cast iron drain in my basement.

I'm going to remove my 4" cleanout and run the trap into that fitting.

Here's the difficulty: My cleanout plug is threaded into a bushing held into the bell end of a cast fitting. The threaded cleanout is a little shy of 4" (about 3

15/16) I bought a 4" threaded male PVC fitting but it is about 4 1/4.

Do they make a threaded PVC fitting that will go into a 4" female steel?

Should I just remove the bushing and get the rubber boot that will let me go from the bell end of the cast down to 4" PVC?

[trader4]

Very strange. AFAIK, all pipe fittings are based on inside diameter. So the 4" PVC you have should go into the 4" cleanout threads. Given that you say it misses by about 5/16 or so, I can't imagine what you have. The Fernco type rubber coupling is probably your solution.

[Limp Arbor]

Not exactly. My existing brass cleanout plug is about 3 15/16.

A 4" PVC cleanout plug or threaded male fitting is about 4 1/4.

[trader4]

Not exactly what?

[Evan]

Right...

The clean-out plug was never intended to be used as a perm connection, only to be removable for access to clean out the line if it became blocked...

There is no such thing as a plumbing fitting which will screw into the threads on clean out plug to extend the drain line...

Do this job properly with the correct type of fittings...

This might mean cutting the stack to install the correct cast iron fitting using Fernco couplings on the stack and then transitioning to the PVC piping on the stub of the proper cast iron fitting you just installed on the stack using an additional Fernco...

~~ Evan

[Joe]

You will need to rework your system from the first available cast iron bell end in good shape. I have had success in dealing with older bell ends by using a 9" body grinder fitted with an abrasive cut off disc. Cut a groove all the way around the pipe, then use the disc to cut through about half way. Then tapping a cold chisel wedge into the cut will neatly sever the pipe. If the cut is fairly close to the bell it is easier to get a drill into the lead and oakum seal and get rid of it. The bell can then be cleaned with the usual wire brush on a drill or whatever. At this point measure the bell. Older 4" cast iron was around 4 1/2" inner diameter IIRC, and the newer is 4 1/4". If you just buy the appropriate Fernco fitting at your box store it may work fine with your PVC. If it is a real sloppy fit you will have to call Fernco customer service and they will likely find a dealer somewhere who has the older large fitting. From there it will be standard PVC work, fit up and glue. Good luck.

Joe

[Limp Arbor]

Well I wire brushed and sprayed the cleanout with PB blaster on my way out the door this morning. When I got home I sprayed some more. No luck. The fitting would not unscrew.

No matter, I already bought a 4" hub to 3" PVC Fernco donut. Melted the all the lead out with a brazing torch then had to drill around the steel bushing to get it to come out. Now I'm left with a 4" cast iron hub.

Freakin donut is loose in the hub! I did some googling and it seems that not all hubs are created equal size. Mine is marked 4xH PE but the donut is no way gonna seal.

I wrapped a rag around the donut and got a seal for the night but now I gotta figure some other way to get a seal...

[Limp Arbor]

Your post popped up after I just sent my last one about the loose donut. I'll be going to the supply house sometime tomorrow to see if the have the bigger donut. Thanks.

[DD_BobK]

How about some photos?

Pipe, having a "nominal size" that often bears little relationship to its actual dimensions, is typically controlled by th OD.

That is, most 4" pipe has the same OD. Threaded pipe elements (PVC, brass, steel, stainless) will all fit together independent of wall thickness. (pipe schedule) because the pipe gets thicker by reducing the ID.

As odd as it may sound your threaded plug might be 3-1/2"

Unfortunately cast iron pipe defines this standard because it was never meant to be assembled by threaded joists. Lead & okum(?) was used years ago and now no-hub coupling.

Without a photo its hard to tell what you've got but if no hub coupling should let you do whatever you need to do.

One warning, if the rest of the drain system above this point it cast iron, the section you cut our might be supporting the piping above. Secure the pipes above the cut by blocking well at an old bell joint.

cheers Bob

[Limp Arbor]

Found a tiny old supply house in Trenton that had a 4" XH TY-Seal. for those of you who think I'm dumaas or a nut there is a difference in sizes between 'service weight' and 'extra heavy' cast iron. The ID of the hub on XH is about 1/4" bigger than standard service weight hubs.

see pages 14 & 15 of this pdf

I now know more about soil pipe sizes than I ever wanted to know.

Shout out to Perlstein plumbing - second time they bailed me out.

[Colbyt]

Actually that is not true.

There was an adapter sold at one time that did exactly that. I think I saw it at an online plumbing specialty store just a year or so ago. The one I removed from service went from a 4" CO to 2" female thread.

I do however agree that cleaning out the hub and using a rubber donut or cutting the pipe and using a Fernco is the better approach.

[DerbyDad03]

I actually know of one installed in a basement bathroom where the homeowner added a sink to a bathroom that previously only had a shower and a toilet...and a clean out in the slab.

IIRC it took 2 reducers: a cast iron 4" OD to 3 1/2" ID (female) reducer that screwed into the clean out, then a cast iron 3 1/2" OD to 2" ID (female) that accepted a threaded PVC adapter into which a 2" PVC drain pipe was glued.

I'm not sure why a rubber donut wasn't used.