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

**Man** · 06-05-2012, 08:41 PM

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

**toolaholic** · 06-05-2012, 09:19 PM

Fernco makes these couplings. What You should have done is C.I.TO PLASTIC.. Fernco #3000-44
Would have been EZ

**Man** · 06-05-2012, 10:43 PM

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).

**toolaholic** · 06-06-2012, 06:01 AM

Read on oakum and lead wool ! You can do it ! Good luck Tool

**Tom Sawyer** · 06-06-2012, 06:23 AM

Lead wool is a no no here unless you melt it in your lead pot first.

**toolaholic** · 06-06-2012, 06:43 AM

Originally Posted by Tom Sawyer

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.

**jadnashua** · 06-05-2012, 09:20 PM

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.

**cacher_chick** · 06-05-2012, 09:22 PM

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.

**jadnashua** · 06-05-2012, 10:04 PM

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.