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Ptron 04-20-2010 11:22 AM

Changing toilet rough in
I want to move a toilet back two inches. It currently has a 14" rough-in. I have the bathroom floor out and the flange looks to not be in the best shape anyway so why not.

Normally, I would guess the best way to this would be to cut it off at the horizontal section and fernco some new pvc in but that T that goes to shower looks like it would be any the way. How should I do this?

fabrk8r 04-20-2010 11:36 AM

Install 2" offset closet flange and just use chain to snap vertical C.I. and use Fernco coupling

Ptron 04-20-2010 11:49 AM

Sounds reasonable. Are those offset flanges any more prone to clogging?

zep 04-21-2010 12:45 AM

Not at all. It essentially gets you where you need to be. Go for it

Ptron 04-21-2010 04:19 PM

The Fernco at I saw at the store today was only about two inches long, i.e. it only overlaps each pipe by about an inch is this normal? I was expecting more. I guess it would be enough if everything's solid.

As long as I'm careful to cut straight, I can cut the cast iron with a sawzall can't I? I don't have a chain cutter and I don't really feel like dropping 40 or fifty bucks on one when this is probably the only thing I'll ever use it on.

Jim F 04-21-2010 04:39 PM

The chain snappers can be rented. Don't know about the sawzall, I've never tried it. You will probably be using one of those no hub couplers like the 2" one showing in your picture, but larger diameter.

Alan 04-21-2010 10:02 PM

Sawzall can cut cast iron pretty easy. They make specific blades for cast iron (diamond impregnated) about 20 bucks each though.

When using a fernco, the pipes should come into contact with each other. . . Not sure what you're talking about with the 1" overlap though.

Ptron 04-21-2010 10:55 PM

Sorry, what I meant was the coupler slides over the raw end of the pipe about an inch. The Fernco I saw at the store, and it was an actual Fernco brand coupler, looked like these: It had that rib in the middle that keeps the two pipes from touching, but they come pretty close.

Anyway, I'm considering the original Idea of cutting at the horizontal except about two inches from the vertical stack. The reason: the drain looks like it may have sagged over time and is sloped ever so slightly the wrong way so that the elbow is the lowest point.

I've heard ther are ways to attach the PVC right into the cast iron joint after drilling out the lead seal. Is this what they're talking about?:
They general idea sounds promising but that in particular looks a little sketchy to me. Plus it looks like it reduces the size of the pipe to 3" and that doesn"t seem desireable to me.

oh'mike 04-22-2010 06:05 AM

Reducing the toilet piping to 3" is just fine! If you can get the old fitting out of the iron hub--that is the way to go.


Ptron 04-22-2010 01:44 PM

Will the 3" diameter be wide enough with the shower drain T-ing into it?

I've been trying to do some research on joining PVC and cast iron and it's only confusing me. Here's what I've found:
On using a coupler:
-A lot of people say to use a no-hub connector, but...
-A few people say the pipes being joined need to be the exactly the same or they won't work properly, so a regular fernco should be used.
On running the PVC all the way into the old cast iron hub:
-I haven't found a fitting/adapter that I'm sure is right for this. Are those fernco donuts really the right/best way? Still feels a little sketchy to me but I could get over that.
-Some people suggest installing the PVC in a similar fashion as cast iron; packing in okum and then lead wool or even poured lead (but cooling quickly with water). I even saw one suggestion to (if code permits) pack in okum and then plumber's epoxy.

So now I'm confused. I want to do what's best and most reliable. Not necassarily what's easiest.

SuperPlumberGuy 04-22-2010 02:29 PM

The best way would be to redo it in pvc and tie in with a poured lead and okum joint. The joint does not need to be and should not be cooled quickly. I do not think this is a DIY job though. I think your second best option would be to cut the pipe and use a fernco. I would not recommend touching the hubs if you are not going to do a poured joint.

oh'mike 04-22-2010 04:59 PM

There is a rubber doughnut that will go inside the hub and has a hole for the three inch pvc.

I detailed the method in a post about two months ago. I'm to busy to look it up now.--check through my older posts--the poster was converting from copper into iron--to pvc into iron.


Ptron 04-22-2010 05:51 PM


Originally Posted by oh'mike (Post 432139)
I detailed the method in a post about two months ago. .--check through my older posts--

Thanks. Here it is:

Ptron 04-24-2010 02:30 PM

Well this is gonna be tight. Even with a street elbow and the hub of the 3x3x1.5 tee butted right up against the donut, it's questionable whether I'm going to get the flange moved back two inches from it's current location. Kinda hard to tell for sure without actually doing it so that's what it may come down to. If it doesn't work I may get stuck redoing it with an offset flange. Might have to reconsider just going with the offset flange in the first place and living with the slight back slope in the horizontal.

Ptron 05-20-2010 10:14 AM

What is the typical tolerance for a rough in?
I'm setting the rough-in without a finished wall. I have pretty good idea how thick the wall will be but I'd like to know how much room for error I have (Hopefully without going down to menards and measuring all their toilets). Can anybody tell me what, in their experience, is typical for the distance from the bolts to the true back of the toilet? It occurs to me that this is probably a little more imprtant for a one piece as a two piece has some flexability.

Got the new PVC joined to the cast iron using a Fernco 4x3 donut. It was a little hairy as I discovered only after I got the old pipe out that there's more than one size for 4" cast iron...and of course I don't have the common one. The donut I had was too small by a good 1/4". I had to special order a 4x3 donut made for XH(extra heavy?) cast iron and use the toilet at my friends house in the meantime. Luckily she's only a block and a half away.

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