I am remodeling the bathroom and have some questions about hooking up to my sewer line.

It's a 1940s house on slab foundation. I removed the tub and jack hammered up the floor and found where the previous owners had used a flexible 2" to 1.5" reducer to connect black abs from the tub and vanity to the metal elbow which comes out of the 4" main sewer line which is also metal.

All this plumbing is located right under where my shower is going to go, and I'm not sure the correct way of attaching black ABS to old rusted metal sewer pipe. The flexible couplings are ideal, except they are not supposed to be buried, and I am going to have to fill the hole with cement when I'm done.

Actually, rubber flexible coupling are designed primarily for underground work.

In my state, they are illegal for everything but quick repairs.

In Massachusetts, you need mission style clamps (shielded couplings) to make connections (see pic.) or you could also use the 4 band no hub clamps pictured below. Mission clamps are primarily used to transition from cast iron to plastic pipe... so will work nicely here. Would order (2) 4" ABS plastic x 4" cast iron mission clamps... make transition between disimilar pipes nicely (sold mostly at PLUMBING SUPPLY HOUSE).

To install a wye fitting into a main drain line you would:

1) install a 4 inch piece of ABS pipe into each end of a 4" x 2" wye. Then measure this wye with pipe END TO END. Let's say you got 12" end to end.

2) then measure and make 2 marks on 4" pipe that are 12.75" apart. Then want to cut the cast iron pipe using the newest cast iron cutting technology... the LENOX diamond sawzall blade and a sawzall.

Why the extra 3/4"? Because that 3/4" will allow you to make LESS than perfect cuts as well as allow the rubber couplings to be installed, folded back on themselves and let you install the wye with pipe in between...fold rubbers back onto pipe, then install the SS clamps and tighten down.

The shower will need an 1.5" vent and a 2" ptrap. The drain pipes should not end up in the concrete..should cover all with dirt to within 3" of floor, then install concrete. Also note that you want to BOX out the pipe (say 6" x 6" box) for adjustments if needed and to accommodate the bottom of the shower drain assembly connected to new shower.

Last note... if installing a pre-molded shower base/pan... then want to install this base in a modified thinset mortar or a perlited gypsum plaster to reduce the squeeks/motion that occur with these type of showers.

If custom shower pan.. then no need for above! If custom shower pan, let us know as we have some good web sites to direct you, too!

Hey, if this helped please RATE THIS ANSWER. Thank you.

Let us know what you think... Mark

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Originally Posted by jdraughn

I am remodeling the bathroom and have some questions about hooking up to my sewer line.

It's a 1940s house on slab foundation. I removed the tub and jack hammered up the floor and found where the previous owners had used a flexible 2" to 1.5" reducer to connect black abs from the tub and vanity to the metal elbow which comes out of the 4" main sewer line which is also metal.

All this plumbing is located right under where my shower is going to go, and im not sure the correct way of attaching black ABS to old rusted metal sewer pipe. The flexible couplings are ideal, except they are not supposed to be buried, and I am going to have to fill the hole with cement when im done.

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If you wish to connect plastic pipe to cast iron underground then purchase a No-Hub Coupling,(see image) in the correct pipe size. Good luck, Tom
(Good morning Mark! I posted right on top of you)