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Old 11-20-2013, 10:41 AM   #1
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Cutting cast iron - sewer gases?


Quick background: redid basement, moved tiny bathroom to better location. Where the old toilet was is now in the corner of the laundry room and is perfect access to the sewer line out to the street. I want to put a PVC cleanout access in place of the old cast iron toilet flange.

The easiest way I see to cut out the old flange down about 4-6 inches without busting up a lot of concrete is from the inside with a Roto Zip and a cut off disc. Yes, I realize this will take awhile.

My question is: how worried should I be about the sparks and the sewer gases going boom? I am on city sewer and the main stack going up through the roof is only about two feet further upstream. Should I at minimum shove an old towel under where I will be cutting, or do I have to be more airtight than that?

Am I being overly paranoid or properly cautious?

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Old 11-20-2013, 11:59 AM   #2
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You need to do it really from the outside with a angle grinder, with a cutting blade. As for sewer gasses, they are not going to be as high as you think. The room if it is ventilated while working in there, and you flush the lines with water, you will not have a high concentration.

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Old 11-20-2013, 12:09 PM   #3
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Thanks for the feedback.

I am hoping to cut from the inside, hence my concern with sparks and sewer gases. I don't want to have to have to break away so much concrete to get at it from the outside with an angle grinder. We will see.

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Old 11-20-2013, 02:22 PM   #4
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You are over worrying about this. As for cutting from the inside, you will never be able to and make it, so that you get a good fitting for the new flange.

You are best to cut the concrete away from the fitting, use a angle grinder with a cutting blade, or pull the lead and oakum rope out, to put in a Fernco gasket and new Closet Flange. Worse case scenario, you run into the issue of the piping being rotted when you start, and you have to cut the floor back far enough, so that you can replace all rotted dwv.
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Old 11-20-2013, 02:25 PM   #5
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You will still need to expose the outside to get a coupling on to connect to the PVC. I have not seen a PVC to cast coupling that went on the inside.
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Old 11-20-2013, 02:36 PM   #6
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Quote:
Originally Posted by joed
You will still need to expose the outside to get a coupling on to connect to the PVC. I have not seen a PVC to cast coupling that went on the inside.
I'm on my phone and too lazy to look for a link so check out Sioux Chief.com for floor clean outs that push on. I believe they have them.
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Old 11-20-2013, 02:42 PM   #7
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You've got nothing to lose by trying to cut it from the inside. As joed has stated, you will need some room for the coupling and room to tighten the clamps.
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Old 11-20-2013, 03:30 PM   #8
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I know I will need some room to slip a fernco over and tighten it up. But that will be a lot less concrete cutting than having to cut the whole flange from the outside.

I will look into the slip on E.

This is this weekend's project, so I will let everyone know how it goes.

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Old 11-20-2013, 05:24 PM   #9
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How much concrete are you saving by not cutting an extra 10" of hole? Maybe three shovel fulls.
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Old 11-20-2013, 08:31 PM   #10
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Quote:
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How much concrete are you saving by not cutting an extra 10" of hole? Maybe three shovel fulls.
Yeah, the hassle of trying to cut that pipe from the inside is a LOT more trouble than just renting a jackhammer and busting it up. No doubt a lot quicker too.

Is there even going to BE enough room inside the pipe to get in there with a cutoff wheel on a rotozip?
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Old 11-20-2013, 11:11 PM   #11
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Straight shaft high speed cutter, we do it all the time, be careful heavy gloves and eye protection.
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Old 11-21-2013, 08:18 AM   #12
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Its not the concrete, its the dust/mess that is the issue.

Yes, thinking what Jav mentioned.

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Old 11-21-2013, 12:24 PM   #13
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Quote:
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Its not the concrete, its the dust/mess that is the issue.

Yes, thinking what Jav mentioned.

B
Put up plastic on four sides of the work area, will keep the dust to a minimum.

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