What tool should I use?

I have a plumbing stack that is a 3" cast iron pipe inside a concrete block wall. The concrete block wall was chiseled out to make room for the pipe when the house was built.
I am moving a sink and hired a plumber to move the drain. The lav drain ties into this stack. To move the lav drain means he has to cut the vent pipe where the tie in will be. However, when I pulled back the sheet rock and exposed the pipe, I found the entire cast iron pipe from top to bottom was compeletly filled in with solid concrete. So 30 years ago they chiseled out the block wall (this is an internal block wall separating the bathroom from the garage) for the pipe about a 12" opening, then the pour solid concrete over that opening.
The plumber told me I need to expose the cast iron pipe, a 4" clearance all the way around the pipe from the slab to 2 feet high so he can work.
So now I am wondering what I need to do. I already tried a hammer and chisel and after half an hour I did not make too much head way so I think I need an electric tool to help.
I am concerned about using doing something that may damage the pipe. The plumber told me if I use an electric chisel or jack hammer I may slip and break the pipe, and if I did the cast iron will crack longitudinally and if that happens I may have to replace the entire CI pipe so I need to be very careful.
I thought about using a hammer drill with a largest possible masonry bit (1") and drill holes every 2 inches all the way in and try to chisel chunks of it out? The block wall is 4" thick so the concrete fill is 4" thick. Will this work?
Or should I get an electric chisel?
Thanks in advance,
MC
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A hammer drill is an electric chisel if you turn the little dial to chisel only mode. Drilling a bunch of holes is fine, too. Either way. Drill 1/2" holes spaced 1" to 1 1/2" apart 4" away from the CI pipe. Drill all the way through the wall on either side of the pipe. Then use the chisel mode to chisel away what you want to get rid of.
R
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wrote:

Thanks R,
I have a mickey mouse hammer drill - a Mikita HP-1501K and I don't think it has a chisel only mode, only a regular drill mode and a hammer drilling mode, I think I need a meaner tool right?
I think my only option is to rent one from HD or somewhere.
Someone told me concrete chain saw but I will be concerned with such tools if I have not used one before.
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It might be worth going to *real* rental shop, not a borg, with an explanation and maybe some pictures. Those guys will know what tool to use and will have a much bigger and better selection than any borg.
Try an American Rent Tool near you.
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Not at first, score a line (fairly deep) to define the zone of removal. Use a beater skil saw with a diamond blade or a 4.5" grinder. I would suggest a Hilti segmented blade (no concern out chipping).
If you can get to both sides of the wall drill through at the "corners" of your cut & score again from the other side.
Now start your drilling exercise on the side of the score cuts away from the from the pipe. You can actually drill 1" holes pretty close together. Don't be worried about taking out too much of the concrete, you're going to have to fill it back in anyway.
Once you have a decent sized "swiss cheesed" zone; 2 holes wide x about 3 or 4 hole long, you can switch to electric chisel, "jack hammer"
Hilti makes some great tools that are varible speed, switchable blow ("little" hammer or "big" hammer), selectable rotary hammer or hammer only. Rent or borrow one
The key is clean out your swiss cheesed area, now start chipping the concrete on the non-pipe side of the cut into this "hole". By having a hole to chip into the concrete will fail in tension and come apart fairly easily. You should make good progress using this technique, demo'ing concrte with a "free edge" always goes much faster.
If you want your can drilling more 1" holes around the perimenter of your cut. When you have the section of pipe that is encased in concrete free from the rest of the wall, you can carefully (use little hammer) chip the concrte on the pipe away....
chip away from the pipe (shallow angle) into your perimeter void. You an also use that 4.5" grinder as well.
Cast iron is brittle but its not glass.
Oh, use a shop vac for dust control...you'll need it for the scoring cuts.
cheers Bob
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wrote:

Thank you Bob! The other side has a bunch of shelves right now I am trying not to break it. However the plumber said 4" all the way around so I might not have a choice since it's a 3" pipe and the wall is only 4" thick.

If I buy or rent an electric chisel, should I used a flat blade (one that looks like a big flat head screw driver) or a pointed one?

OK I understand.

Unfortunately. It's going to be a mess.

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On Fri, 19 Oct 2007 03:29:02 -0400, "MiamiCuse"

Why would anyone encase a stack pipe in concrete?????
WIth that said, if it was my job, I'd find a way to run pvc up into the attic, leave that pipe alone, and in the attic tie the pvc to the cast iron. (I cant imagine the stack in concrete in the attic.
Just build out the wall with 2x3's and you can run a inch and a half pvc between these 2x3s. The wall will add a little more insulation too.
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wrote:

I don't know. I know it is NOT for support, because the concrete goes up to about 6.5 feet and stopped and nothing from there up to ceiling.

Well the lav has to drain and so has to tie into the pipe underneath, and the most convenient spot is sideways to that CI stack. Of O leave that alone, then yes I can do a PVC up and tie in up in the attic, but I need to run that PVC down to drain somewhere below the concrete slab, in that case I need to open up a hole on a 4" slab and dirt up the dirt to expose the CI pipe below and put an elbow in, so either way I am breaking 4" thick concrete, I am not sure it would save much time this way. But I will continue with your thought to see if I can think outside the box a little.

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put the concrete back when your done, between garage and home its a firewall and required.
why not run a new line down and up and connect outside of the concrete area.
disturbing this concrete you may find the cast rotted and have to replace the entire thing. that may or may not be a bad thing
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On Fri, 19 Oct 2007 03:29:02 -0400, MiamiCuse wrote:

Not knowing all the details of your building, I would probably look to see if an alternative stack could be installed. If possible, you could abandon the original. Might be cheaper, but this again depends on your building's design and your situation.
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franz frippl wrote:

ff:
Why not let the plumber do it? <EG>
G P
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Sounds like your plumber is going to break the cast iron pipe and put in a no hub T of some sort to hook up your lav. If thats the case he will probably use one of those cast iron pipe snappers which means the chain needs enough clearance to go around the pipe. Or he could sawzall it. Either way it sounds like a big job. Is this a solid concrete wall or a cinderblock wall?
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It is a block wall, but the area around the pipe is solid concrete,
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