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Thread: When connecting 4" ABS sewer line to Cast Iron, how deep is deep enough?

  1. #1
    DIY Junior Member Man's Avatar
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    Question When connecting 4" ABS sewer line to Cast Iron, how deep is deep enough?

    I'm replacing 4" Cast Iron Sewage plumbing with some ABS. I was able to replace a section of old cast iron with ABS and connect the new ABS pipe into the female gasket on the Cast Iron side. I believe the depth of the rubber gasket was about 2 and 1/4" deep on the inside of the old pipe. I was able to get the ABS to go about 1 and 1/2" to 1 and 3/4" into the cast iron. I'm wondering if that is deep enough. Afterwards I noticed that the cast iron pipes a re about 1/16 narrower than the ABS which explains the really difficult time I had getting to 1 1/2" of connection. I used a lot of soap. I also sanded a slight bit off the edge of the ABS to help it go in. Will that be enough to keep the sewage going downhill? This is under my slab floor so I have to know for sure before I pour the concrete. Do I cut it back out (not able to remove it) sand a lot more off and try again?

    Note* it took two men pushing with all our strength on a six foot lever (huge steel pipe) to get the ABS to budge the 1.5 inches.

    Thoughts?

    Thanks,
    MAN

  2. #2
    General Contractor Carpenter toolaholic's Avatar
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    Fernco makes these couplings. What You should have done is C.I.TO PLASTIC.. Fernco #3000-44
    Would have been EZ

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    Retired Defense Industry Engineer jadnashua's Avatar
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    While the big-box stores only typically carry one or two sizes for any application, in truth, there is no real standard, so you have to measure carefully and get the right one. Sounds like yours is slightly too large. Fernco makes them in (I think) like 1/16" exterior increments for just the right fit.
    Jim DeBruycker
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    Test, Don't Guess! cacher_chick's Avatar
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    I have a feeling that you might have the wrong coupling.

    This is the coupling you should be using- http://www.fernco.com/sites/default/...df/1056-44.pdf

    It is rated for pipe that is 4.02 to 4.65 O.D.

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    Nope, sounds like he's using a donut, not a coupling. The donuts for any sized plastic pipe come in numerous OD's to fit various sized hubs. Every manufacturer makes theirs a 'nominal' size, and that can vary both between normal and heavy duty as well as within the same type.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6
    DIY Junior Member Man's Avatar
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    Thanks for the quick reply. I believe the Fernco couplings would work perfectly in a C.I. pipe to ABS pipe scenario. However I have an ABS pipe to C.I. female (hub?) with a rubber seal, and it happens to be a Y so I have to keep it in place.

    My question comes back to, would you settle with 1.5" to 1.75" out of 2.25"? I think I've got a really good seal and have used it for a few days with no hint of a leak. The seal within the cast iron "hub" seems to narrow once you get about 1.5" in, and I can only imagine with the old C.I. pipe, it fit just fine. However due to the larger diameter of the ABS, it seems to fit quite snugly within the first 1.5" depth and is too big to make it further into the seal. The pipe isn't going anywhere and I would think this current connection would hold up pretty well.

    To replace it, I would have to cut out the 2' of ABS and an elbow and cleanout Y, and start over trying to shave off enough of the edge of the ABS that it would make it past the 2nd seal (or rather, the narrower portion within the C.I. seal).
    Last edited by Man; 06-05-2012 at 11:15 PM.

  7. #7
    General Contractor Carpenter toolaholic's Avatar
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    Read on oakum and lead wool ! You can do it ! Good luck Tool

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    In the Trades Tom Sawyer's Avatar
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    Lead wool is a no no here unless you melt it in your lead pot first.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    General Contractor Carpenter toolaholic's Avatar
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    Quote Originally Posted by Tom Sawyer View Post
    Lead wool is a no no here unless you melt it in your lead pot first.
    I do it here ! #1 Poster didn't give His location,and that's fine. #2 I'm guessing this is a boot leg project.

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    Moderator & Master Plumber hj's Avatar
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    lead wool is an apochryphal item. Everyone says to use it, but I have never seen anyone actually hammer it hard enough to make a homogenous mass. Oakum and melted lead, (ingot or melted lead wool), are the only sure seals. The PVC should go ALL the way to the bottom of the cast iron hub to make a good seal. Since that hub was NOT intended to have a rubber gasket in it, (it was before Ty-Seal with its rigid specifications), there was no need for a "standardized" dimension.
    Licensed residential and commercial plumber

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    DIY Junior Member Man's Avatar
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    Thanks HJ for the clarification and explanation. Regarding the rubber seal, it was in place with the previous C.I. pipe. Are you saying that the rubber seal was previously, historically not used in plumbing and that for a true seal, Oakum and melted lead were used? I do have a problem with roots getting into the rubber seal and tearing the pipe apart or filling it up (thus why I've replaced the rotten pipes with ABS - I understand an ABS glued joint should be much more root resistant). In my case I think I will take your advice and make the pipe fit all the way into the rubber seal using methods discussed previously. If there are different pipe sizes by 1/16" will HD/Lowes carry it or do I need to go elsewhere? Thanks

  12. #12
    General Contractor Carpenter toolaholic's Avatar
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    Quote Originally Posted by hj View Post
    lead wool is an apochryphal item. Everyone says to use it, but I have never seen anyone actually hammer it hard enough to make a homogenous mass. Oakum and melted lead, (ingot or melted lead wool), are the only sure seals. The PVC should go ALL the way to the bottom of the cast iron hub to make a good seal. Since that hub was NOT intended to have a rubber gasket in it, (it was before Ty-Seal with its rigid specifications), there was no need for a "standardized" dimension.
    I use it with great success! Next time I do it I;ll invite You for the 10 ft head test.

  13. #13
    Retired Defense Industry Engineer jadnashua's Avatar
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    A leaking seal will attact roots, and any opening will allow roots in. The best connection is a leaded one. Note, the oakum makes the seal, and the lead keeps it in place and intact. As I said, Fernco makes LOTS of donuts to accommodate different sized hubs. If you had the right one, the pipe would have fit in all the way and made a proper seal.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  14. #14
    General Contractor Carpenter toolaholic's Avatar
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    Here's a lil different idea for roots at a connection. At back fill time do this at EACH end of the repair coupling . Install 1" Pvc pipe ,open end resting on each joint of repair. Back fill and put top end caps Just below surface. Once each spring mix a hot tea of copper sulfate and water. pour down pipes ,put cap back. Done it for years at My own home. works great! My personal idea.

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    DIY Senior Member DavidTu's Avatar
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    Take careful measurements... CALL FERNCO they will be able to fabricate an exact match most likely... they have many moulds that they do not necessarily keep stock for and you may probably will not find what you need off the shelf... but they can get it to you probably within a week's time. That's my experience.

    It sounds to me like you are putting the donut on in reserve order... I believe I've put the donut on the ABS and then used a mallet and wood to tap the donut into the CI hub. Even with soap I've never had an easy time getting the donut in. Sounds like you are putting the donut into the hub and then inserting the ABS pipe. Check Fernco's site for instructions.

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