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Thread: What to do with this cast iron flange and pipe?

  1. #1

    Default What to do with this cast iron flange and pipe?

    I got a pointer here from the John Bridge tile forum.

    We are remodeling a guest bath and I have some questions about the 50 year old toilet plumbing. We've got 4 inch cast iron pipe with a solid iron flange that appears to be soldered to the outside of the pipe. The flange is completely solid - there are no places for it to affix to the floor, just the two toilet bolts that appear integral. The pipe seems solid though the lip closest to the front has corroded down a bit, I don't know if that affects its integrity. The flange was sitting lower than the tile, which itself was on top of the original linoleum, and did not appear to be supported by any kind of subflooring to speak of.

    There is evidence of water damage to the plywood subflooring as you can see, though we never saw any leaks above the tile (probably because the flange was lower, right?) Given the whole setup you see here, including the access underneath, would we need to replace the flange and/or soil pipe, or can we make this work? The new tile we plan to put in would put our finished floor level flush with the old flange.

    Thanks in advance for any ideas.
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  2. #2
    In the Trades Gary Swart's Avatar
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    It appears that the cast iron under the floor is in good condition. I believe I would stub the pipe off just about where that rust spot is and replace with a banded coupler, a short piece of PVC, PVC closet bend, another short piece of PVC, and a new flange. I would not cut the PVC coming up from the closet bend nor attach the flange until the finished floor was down. You obviously need to do some repair on the sub floor, and the flange should set on top of the finish floor (not flush) The new flange will need to be screwed through the finished floor and into the sub floor. The current flange did not need to be screwed down because it was leaded to the cast iron so it was very solid, but the new flange could flex a little. Now, this is not the only way the job can be done, but it is something you could probably do yourself. The most difficult part of it is cutting the cast iron pipe. Best to rent a chain pipe cutter, but a grinder will also work. I have never had success using a recip saw although some guy apparently have cut cast with a special blade.

  3. #3

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    Gary, thanks. We're weekend warrior DIYers and I'm nervous about cutting the pipe ourselves. Would you have a sense of roughly how much time it should take an experienced plumber, so I can get some estimates? I think we'd be fine to cut the pipe/put in the flange after the floor is down, but I would want help up to that point.

  4. #4
    In the Trades Gary Swart's Avatar
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    Sorry, can't give you much of an opinion on cost. It looks like a pretty straight forward and simple job, but there is always the risk of the unforeseen problems. Then, the cost will depend on the rates in your area. These can vary widely for place to place, and even from individuals. In addition, a "real" plumber might very likely opt to just reposition and replace the flange with cast iron which is quite a bit beyond what most of us diyers are capable of doing. Suggest you have a two or three estimates.

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    There are at least three ways to cut cast iron: soil pipe cutter (snapper), grinder preferably with a diamond blade, reciprocating saw with appropriate blade. It looks like you have enough room to use a soil pipe cutter - rent one, and once you're home, it will take you about 2-minutes once you figure out how to use it (ask at the rental place). All other options will take longer and require more skill.

    Another alternative is to remove the pipe from the hub - drill out the lead into swiss cheese, then pry it out, then rock out the stub. They make a rubber donut that fits into the hub and pvc fits into that. Hardest part of that is getting the right size.

    Another alternative is where you'd want a plumber to deal with...you could remove the existing flange, do your new floor, then have a plumber install a new flange on the CI. There are DIY'er alternatives (one is a Twist-and-set flange), but the best is a new leaded flange.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Default flange

    Why not do it the correct and easy way. Call a plumber to remove the flange and install a new one on top of the new flooring, It should take about 20 minutes if he is halfway competent.

  7. #7
    DIY Member CharlieM's Avatar
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    +1 hj's suggestion.

    I had the same situation.

    Had my plumber remove old flange. I tore out and replaced subfloor, then membrane and tile. My plumber came back and leaded in a new flange on top of the tile. The longest time was heating the the lead pot.

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by hj View Post
    Why not do it the correct and easy way. Call a plumber to remove the flange and install a new one on top of the new flooring, It should take about 20 minutes if he is halfway competent.
    As I said in my post, this is the best way, but the others are acceptable in code and performance.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  9. #9

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    Thanks for all the ideas. I'll give a couple of local plumbers a call. I don't want to rip out perfectly good pipe if it's not necessary, but don't want to miss an opportunity to correct a system that's not up to par.

  10. #10
    In the Trades Gary Swart's Avatar
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    A plumber who can examine the situation in person, on site may determine the only thing that needs replacing is the flange. Just because there is a bit of rust on the exterior of some of the cast iron does not mean it needs replacing. It's just that for a DIYer, cast iron is difficult to work with so transition to PVC is frequently done. I think you are headed in the right way.

  11. #11

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    Thank you all for your input so far.
    I spoke to a couple of plumbers, neither of whom will do a new lead/oakum joint on a CI flange. And can't recommend a plumber who would do that. I guess it really is a dying art. Plumber quoted ~ $300 to replace the CI with ABS. We're mulling over our options and I'd welcome some feedback.

    - If we can remove the old flange, and the CI pipe is solid, is a new CI flange with a compression insert a viable option? It seems this would be the easiest DIY option, but I don't want to do something that's destined to fail down the line.

    - If we go the DIY route and cut into the CI pipe to replace w/ ABS or PVC, is it better to use a Fernco coupler to drop the diameter to 3" at the connection, or better to use a no-hub connecter then drop down the diameter with a 4x3 elbow?

    - Overall it's a very short run that needs replacing - probably less than 5" of straight pipe needed on the horizontal. I am wondering how you achieve the necessary drop if the bend is a 90 degree turn. Do you just put the pipe in at the necessary angle? Will it seal up okay if it's angled to connect to the cast iron?

    Thanks in advance for your help (again).

  12. #12
    Retired Defense Industry Engineer jadnashua's Avatar
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    3" may be easier to work with and give you a little more leaway as the 90 may have different radius than the CI one. Do not use the rubber 4-3" coupling...won't pass code. Use a no-hub connector to convert the pvc to CI, or, if you go all the way back to the next hub, take th epipe out of the hub and use a Fernco donut to make the conversion.

    A 5' section of CI is heavy...don't let it fall on anything, it will hurt!

    The twist-and-set flange should work if the inside of the pipe isn't too corroded.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  13. #13

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    Wanted to come back and update - after wrestling out the lead and taking off the old flange we found out that we couldn't get a twist-n-set to go in. Wound up cutting the cast iron near the hub and putting in ABS.

    The flange I bought doesn't want to push down on the elbow, and I don't want to cement it up unless I know I can get it snug. Is there a way to try to gently sand or otherwise shave either the closet elbow or the inside of the flange so it will seat? Or, back to the store for a new flange?

  14. #14
    Plunger/TurdPuncher kingsotall's Avatar
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    The ABS glue should allow the fitting to get full engagement. Dry fitting always leaves a gap that is eliminated once glue is applied to the fittings before they are connected.

  15. #15
    In the Trades Gary Swart's Avatar
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    ABS and PVC can not be dry fit. The reason is these joints are solvent welded not glued. The so-called glue actually is a solvent that briefly melts the top layers of the pipe and fitting and while these surfaces are liquid, the pieces will slip together. The solvent then dries and the joint is welded together much the same as welded metal except the process is done with chemicals not heat. This means you must measure the depth of the fitting and cut the pipe long enough to bottom out in the fitting.

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