Help on removing cast iron flange and replacing with a pvc twist and turn flange


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Old 02-06-23, 01:51 PM
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Help on removing cast iron flange and replacing with a pvc twist and turn flange

I am going to be replacing the section of subfloor by the toilet. I was thinking of removing the old iron flange and replacing it with a pvc twist and turn flange. Would you cut the cast iron pipe right below where the flange end? I was thinking of removing the old iron flange before it starts rusting and it would make the job easier to replace subfloor and install new flange on top of tiles.


 
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Old 02-07-23, 09:26 AM
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I was able to remove the flange with some heat and a chisel. Now that I got a good look at the flange it appears to be brass. I'm not sure of the type of drain pipe it is. I know it is probably 3" but it is not cast iron. I noticed it has a few dents and when I used the hammer to remove the flange I could see that it is not hard to dent or bend. It connects to a hub on a cast iron pipe. I thought this pipe that the flange was connected to was cast iron and I was going to insert a new pvc twist flange inside but now i'm not sure if that type of flange would work or what would work.



 
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Old 02-07-23, 10:32 AM
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I just saw your post from yesterday. I was going to say leave the flange if it's in good condition because it's a lot stronger than a new PVC one.

The light gray pipe that dents easily is lead. Don't lick your fingers. It will need to be removed all the way back to cast iron. Then you can rebuild the drain from the cast iron. The lead pipe is probably held into the cast iron with oakum and lead. You can rip the lead pipe out then use a chisel and hammer to remove the lead seal and oakum packing.


I can't see the end of your cast iron but I assume it has the wide end of the bell. There are two ways you can go. One method you buy a rubber PVC to cast iron adapter which allows you to shove the PVC into the cast iron and the ribs of the rubber coupling form seal. With this method it is important that you properly support the new PVC piping so it can't move or wiggle which a properly installed toilet flange can do.


The second method, and what I prefer, is to cut off the bell end of the cast iron so you just have straight pipe. Then use a no hub coupling (rubber & metallic sleeve with hose clamps) to attach the PVC and iron together. I prefer this method because there is a sound mechanical connection between the two.
 
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Old 02-07-23, 12:05 PM
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I enclosed a picture of the bell so looking at the picture the lead pipe going into the first half of the bell I would cut the straight cast iron pipe close to the 2nd half of the bell and then use a no hub coupling and connect a 3 inch pvc pipe? Could I use a sawzall with a bi metal blade or will I need a cobalt blade?

 

Last edited by PJmax; 02-07-23 at 01:13 PM. Reason: labeled/resized pic
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Old 02-07-23, 01:16 PM
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I labeled the picture. Makes it easier to discuss.

Looks like A is 4".
B is a reducer fitting. Down to 3" or 3-1/2".
 
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Old 02-07-23, 02:47 PM
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Cut just above where it's tabled "B", just past the bell so you have as much straight pipe remaining as possible (but don't make the job harder for yourself just to save another 1/4" of pipe).

You can use fine toothed bi-metal blades. Buy a six pack and you should have a couple leftover if you move your saw position so you use more of the blade's cutting surface. When a blade gets dull go ahead and get a new one because a fresh blade does cut noticeably faster.

When cutting don't let the saw blade bite and shake the piping. The last thing you want is to break a joint in the cast iron loose.

Holding a saw over your head will tire you quickly. I'd remove that one strip of subfloor so you can work more comfortably from above.
 
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Old 02-07-23, 03:08 PM
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Ok I will give it a try. It looks like the pipe just above the bell is larger (probably 4") so I assume it will be okay or better to use 4" pvc pipe to the flange.
 
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Old 02-08-23, 04:54 AM
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Darn, I thought I posted a long reply last night.

Yes, you can use a reciprocating saw with bimetallic blades. Higher quality blades could last longer but it mostly comes down to cost. I would get a 6 pack of bimetallic blades. You'll probably use 3, maybe 4 leaving a couple extra because if you only buy 3 you're going to break or seriously bend one and have to drive back to the store.

When sawing on the pipe make sure you don't let the blade bind and vibrate the pipe. You don't want to break a joint apart and expand your work even further.

Yes, if your main drain is 4" you can extend with 4" PVC. 4" will make it a little tighter getting a 90į fitting and toilet flange in place so just give it a look over before going 4". If you are tight for space you can drop down from 4" to 3" anywhere you want in that area.
 
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Old 02-08-23, 05:39 AM
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Posts are not chronological. There is another thread addressing the chronological problem.
 
 

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