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Old 10-08-2009, 07:18 AM   #1
Willing & Sometimes Able
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ABS/PVC to Cast Iron

I need to tie into existing cast iron sewer main for a new toilet and shower in my basement. There is a 12' run for the shower and a 6' run for the toilet.

My problem is, I have to go below the concrete floor (low ceiling height) and that will bring me below the bell of the cast main. What can I use to tie into it and do I need to protect it from the new poured concrete?

Thanks in advance for any and all help.


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Old 10-08-2009, 05:55 PM   #2
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Hi Canadadan:

You will want to dig out the concrete and dirt to about 2 inches under the pipe for a few feet along the pipe. DO NOT underestimate the importance of this step!! Before cutting into the cast iron, you must support the cast iron pipe above the floor using a hanger (riser clamp) and some 2'x4"s as in the picture below. You could also support under the fittings above the floor, but need to be sure that the fittings/hub can handle the weight...just in case... This can be dangerous work, so just be careful, support the extreme weight above and you will be fine!

Then you will want to cut into the cast iron pipe using a reciprocating saw (sawzall) and 8" bimetal sawzall blade(s) or see if you can find the lennox diamond sawzall blades as these make short work of cutting into the cast iron. Here, you want to use a PVC plastic wye fitting (or ABS plastic if that is what is used in your area) and you want to prime/cement 6 inch pieces of pipe into each end. Then you measure the overall length of the fitting and pipe and transfer that measure PLUS 1/2 to 3/4" extra to the cast iron pipe. The 1/2" to 3/4" extra acommodates a slightly poor cut and the ribs on the 2 clamps you will be using....see image below.

Once the cuts are made you will slide (2) PVC x cast iron SHIELDED CLAMPS (see image) onto the pipe, slide the clamps back out of the way and then FLIP the rubber sleeves back on themselves as in the other picture below. This will allow you to drop the wye fitting plus pipe into the space and then FLIP the rubber sleeves back in place and slide the clamps over the sleeves. Once the wye is installed to give the correct pitch to the drain line you will tighten the clamps down to correct torque.

Let us know if you have questions on this...

Do you need help working the venting on this bathroom??

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Old 10-08-2009, 07:00 PM   #3
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I'm not sure hoe it is in cananda but in the us you can only run 2" pipe a max of 8' from a trapped fixture and the shower will be a trapped fixture.


What are you using for a vent?
John Wayne once said "Life is tough and it is even tougher if you are stupid"

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Plumber101 is offline   Reply With Quote
Old 10-10-2009, 12:12 PM   #4
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Boston: Thanx for your help. I will be taking advantage of the work by replacing as much of the cast as I can get access to. I assume that I will have to wrap and protect all PVC and joints that will be below the concrete?

Plumber101: Thank you as well. I was hoping to tie into the existing 4" vent that is 7' away from the new basement shower (2' from existing main floor shower) and 18" away from new basement toilet (4' from existing main floor toilet).
CanadaDan is offline   Reply With Quote

basement bathroom , concrete floor plumbing

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