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Thread: replacing cast iron sewer with plastic

  1. #1

    Default replacing cast iron sewer with plastic

    I am trying to replace some old (perhaps 60 or more years) cast iron sewer line that rns into my basement with plastic. I went to Lowes and they have like 3 different brand and colors of pipes that says "sewer" on them .. they were white, green, and gray in color .. i ended up buying the white one because it was the cheapest ($8 / 10 feet pipe).. here are my questions:


    1- Do the colors mean anything? What type do u recommend?

    2- I have 2 use those black flex rubber coupling that have those screw rings (sorry don't know proper name) in a couple of places .. how tight can i make them? i am afraid that i should have bought the more rigid pipes since i have to use these type of coupling

    3- what is the best way to cut the old cast iron pipe .. i am afraid that it would crack .. specially at the end where it eventually goes under the ground ..

    Thanks for your help and suggestions.

  2. #2
    In the Trades Bob NH's Avatar
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    If you bought white sewer pipe that doesn't say "Schedule 40" or DWV; if it is that thin white stuff that is similar to the kind that has holes in it and used for french drains, then you should take it back and get some that at least says DWV.

    Another way you can check is to see if it fits a DWV fitting such as a Wye or Tee.

    And your clamps should have a piece of metal that covers the full length of the rubber cylinder.

    If it is the right pipe, you will not be able to break it with the clamps.

    You can cut the pipe with a chain cutter/snapper device, or you can cut it with an abrasive wheel on an angle grinder. I have also occasionally cut a piece with a very good and heavy duty saber saw. You could probably also do it with a SawZall. I would be more inclined to use a saw or grinder device near the concrete where the consequences of breaking the pipe into the floor are severe.

  3. #3

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    Bob . .thanks for the reply .. no it does not say DWV or schedule 40 .. it does say "sewer line" on it .. i guess i just return it and get the good stuff to be on the safe side .. i am selling the house and want to make sure it will work later .. what does DWV mean anyway?

    Also, a couple of my clamps have that metal piece around them so i should be good there .. but i am also using a flex rubber 3 way (t shape) and U shape one .. r those ok to use?

    also, i am having a very hard time finding all the pieces that i need .. like transfering a 2 inch pipe to 4 inch .. is it because lowes oe ********* don't have all the stuff? where should i look for my parts?

    Thanks for all the help.

  4. #4
    In the Trades Bob NH's Avatar
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    DWV means Drain Waste Vent.

    I'm not a pro at DWV plumbing, and I'm not familiar with rubber Tees and U shapes, and would suspect that they are not acceptable. You should await feedback from the pros in that area.

    You should be able to find 4x2 reducers and such in PVC (the white stuff) or ABS (the black stuff); whichever is used in your region.

    You should search some of the older posts here under plumbing to find some examples and pictures. I'm a little concerned that you are on your way to cobbling something together without knowing the right way to do it. It will look like hell to a new buyer if you don't get it right.

    Those rubber couplings should have metal wrap their full length, as well as screw clamps at the end.

    You would usually use those only where you need to adapt from cast iron to PVC or ABS, and use cemented fittings at all other places. And you can't mix PVC and ABS; use one or the other.

    It would be good if you could post some photos and/or sketches here and get suggestions before you start cutting cast iron.

  5. #5
    Plumber Cass's Avatar
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    You didn't mention how much pipe you are trying to replace and we can't see the scope of the work. By the questions asked I would recomend you get a few estimates at having the work done by a plumber. If nothing else you will have an idea of what amount of work realy needs to be done. Don't be afraid to ask questions. Replacing 1 small peice of pipe could end up being a nightmare if you end up having something go wrong that you didn't forsee and then dont have the knowlage or tools to deal with it.

  6. #6

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    Bob, Cass ... i did get an estimate about 6 months ago and it was about $1500 .. the parts will not cost me more that $200 and i can not imagine taking me (a non-professional) more than 10 to 12 hours, IF I have all the right parts!!!! .. basically .there are 2 iron pipes (one 3" and the other 2") that come from the bathroom and kitchen area from the upper floor (10 feet apart) into the basement where they feed into a 4 inch cast iron pipe that runs almost parallel to the basement floor (well, it is sloped and 20 feet later runs into the ground).. it is this pipe that needs to be replaced.

    .. since the house is being sold "as is" and the buyer is aware of all that is wrong with it, i am just doing this learn something new .. for me it is just a matter of getting the right parts (and learning proper names for the parts) .. i have jumped into much larger projects .. i will try to take some pictures tonight and post .. thanks again.

  7. #7
    DIY Senior Member SteveW's Avatar
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    Why does this section of cast iron pipe need to be replaced?
    Is it corroded? If so, why? What will prevent it from happening again?

    Replacing cast iron pipe is not the best DIY project. There may be unexpected consequences -- like the weight of the pipe from the upper stories of the house causing it to shift when you cut out the bad section.

    Also, if you do use the flexible tee fittings, etc., and one of them comes loose or springs a leak and floods the basement with sewage, the new owners won't be too happy with you, esp. when they learn that the repair job was not up to code.

  8. #8

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    Steve, it needs to be replaced becasue it is the original pipe and corroded .. it leaks .. i see your concern about the weight ... i realize that i need to support the pipes before cutting any section .. maybe it is a bigger project that i am thinking??!!!

  9. #9
    In the Trades Gary Swart's Avatar
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    Cast iron is extremely heavy and is assembled from the bottom up so the weight is supported by the lower portion. Remove that support and above can and will come crashing down. As evidenced by your lack of knowledge about PVC/ABS drain pipes, I think you may be starting a trip you don't want to go on. If the buyer is taking the place as-is, then let him repair the drain if you don't want to hire it a professinal to do it right.

  10. #10
    DIY Senior Member coach606's Avatar
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    Default You can maybe do it...



    It is good advice to be cautious about cutting into your four inch stack. You must buy riser clamps and build a little cage around the pipe to be cut. Use the riser clamps to hold up the cast iron above and below the cut. You don't want that pipe sagging or falling on you.

    Secondly, understand that a lot can go wrong, especially with the snap cutters. If the pipe crushes, you will have to saw it out with one of the methods mentioned previously and it is apparently a huge hassle. I believe the possibility of sagging pipes or crushing the pipe rather than snapping it are the two most serious consequences.

    Having recently cut into my 4" cast iron stack to run a new drain line for a new bathroom I can tell you that you should be prepared for these negative outcomes. However, with advice I was able to do it with no problems. Be sure you support the pipes above and below the cut and rent a ratcheting chain cutter. There is really very little involved in using the chain cutter. Just mark your cuts, give yourself some extra room and then tighten the chain.

    Once you cut out a section of pipe in the stack, Use a pvc wye fitting with some straight pvc pipe glued into the hubs. Then go ahead and use your rubber (no hub) gaskets to connect to the cast iron. Mine work great and I never had any leaks. When you snap the pipe it may not fall right out, even with riser clamps because a bit of weight is still on it. You can make a third cut between the first two, but make it at an angle, Then tap it with a hammer and the piece should fall right out. Be cautious about pieces falling into the cut stack when you use the hammer. I had to retrieve a piece with a telescoping magnet, but it worked.

    I went ahead and cut my own stack because I really wanted to do it and felt I could handle it. Many people told me I should hire a pro, but it worked out okay for me. I went ahead partially because there are no guarantees when doing this. You could have a pipe that crushes instead of snaps even if a pro does it. If your pipes sag for some reason or fall, it could happen even to a pro. Then it'll cost you a lot. I figured I'd do my own because what could go wrong for me could also go wrong for a pro. But luckily, things worked out.

    You could ask the pros here who do this all the time how often a pipe will crush instead of snap, but I think it's pretty rare. It may happen, but I think most pipes will snap. Just be sure you know what you are doing and that you are prepared for any consequences of what you do.

    If you are really ready to accept and deal with the possible outcomes, research it until you feel ready and then go for it. I had some people on other boards who told me I "needed" to hire a pro, etc., for mine, but I just kept researching and when I was comfortable I did it. Took about three hours to cut the pipe and attach the new fitting.

    Good luck. Feel free to ask me questions. Since I'm a DIY'er and I just did it I may better understand your questions than a pro who can't remember what it was like to have the kind of questions a newbie has.
    Last edited by Terry; 01-20-2008 at 09:36 AM.

  11. #11
    DIY Senior Member SteveW's Avatar
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    Quote Originally Posted by switchex

    Also, a couple of my clamps have that metal piece around them so i should be good there .. but i am also using a flex rubber 3 way (t shape) and U shape one .. r those ok to use?

    also, i am having a very hard time finding all the pieces that i need .. like transfering a 2 inch pipe to 4 inch .. is it because lowes oe ********* don't have all the stuff? where should i look for my parts?

    Thanks for all the help.

    Just to be clear about this, there are 2 different types of flexible connectors for DWV pipe. The standard, approved kind consists of a simple "rubber" (probably actually a synthetic material) cylinder, which is covered by a stainless steel band, which is held on by 2 screw clamps. It joins 2 straight pieces of DWV pipe together and is widely used and accepted.

    The fittings you are referring to above are actually whole "joints" -- wyes, tees, etc., -- made out of that "rubber" material. I've seen 'em at the home stores. They certainly look tempting, but I suspect they may not be code (I'm not a pro so don't know for sure). I would recommend NOT using these, unless one of the pros here can vouch for them.

    RE: where to buy "stuff," if you live in a big enough town, you may have access to a professional plumbing supply house like Ferguson's. I've been to my local Ferguson's several times, and while I feel a little like a fish out of water (not being a pro, and it shows!), they have generally been helpful, and they certainly stock fittings, tools, valves, etc. which you will NEVER see at a regular home store. Much better quality stuff in general (and of course more expensive).

  12. #12

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    hire a professional, this work is way out of scope for a DIY. This is plumber grade material.

  13. #13
    DIY Senior Member coach606's Avatar
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    Default maybe, maybe not...

    He could be right about hiring a pro. But like I said, I did mine. The chain cutter is not very hard to use, nor were the riser clamps. Measuring, cutting and gluing in a pvc wye with shielded no hub couplers was also a fairly easy DIY'er job.

    I'd be worried about crushing the pipe near the part that goes into cement, but I'm not sure that's even an issue. Seriously, the snap cutters were EASY to use. Just wrap the chain around your marks and ratchet it tight until you hear a little 'thunk.'

    If you can properly support the pipe with riser clamps and the pipe snaps (as I believe most do) you should be fine. Hey, if you're not comfortable hire a pro. But I think a DIY'er can do it. I don't believe it's way out of scope. If things go well it's actually pretty easy.

    If the pipe crushes, it would have happened to the plumber, too. So you might was well take a shot before calling him. Mine was 80 years old and snapped easy. I think a plumber will try snap cutters first, too.

    If you want to research and are comfortable, it is something a DIY'er can do in my opinion.

  14. #14

    Default Thank you All

    I did the job! the estimate i had for the job was $1500 and i spent less than $200 and a weekend. The hardest job of the project was supporting the 3 inch cast iron pipe that came from upper floor bathroom perpendicular to the 4" pipe in the basement .. i was so afraid that once i cut it, it would come down bringing the upstaris bathromm down with it .. but i put a couple of U-bolts around the pipe and secured it to the brick wall ..

    the chain cutter was no easy to use ... i think the one i rented was a super-heavy-duty .. very very heavy .. the chain it self was almost 2" thick... i suspect there are lighter and smaller ones ..

    the pipe did crash in a couple of places where i was doing practice run (i had to cut it in pieces any wy to dispose of later) .. but it worked fine were i really needed it ..


    This is the proper coupling.

    i did cheat by using the rubber coupling that does not have the metal around it .. only becasue my pipe came 1/2 inch short at the end and the rubber without the metal around is much longer .. but i can easily cut the last piece of pipe o extend it and use the other coupling, if i am against the code

    Thank you all for your help, suggestions, and support.

    I'll be posting my next 2 projects soon. Later.
    Last edited by Terry; 05-03-2007 at 09:24 AM.

  15. #15
    Retired Defense Industry Engineer jadnashua's Avatar
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    Banded no-hub inside, fernco burried where the ends can be supported. The steel support keeps the two ends aligned, the other one can offset things and potentially trap things and create a clog.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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