Connecting 3.5" IPS to ABS for sewer line extension

BigD

BigD

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Aloha folks -

We are researching the possible extension of our CI sewer line in order to add a toilet/shower/vent to the mix. Our sewer ends in a nice clean out about 2' underground running horizontal. The CI itself is quite rusted on the outside - likely due to our proximity to the ocean and the salt content of our sand. (no dirt, just sand!)

We discovered the 4" CI has 3.5" ips so the 4" ABS male coupler didn't work. Trips to Lowes and other stores don't show us ANY threaded coupler solution.

We thought screwing in something would be a MUCH better fit vs the Fernco option. Is there something out there? Specifically what and how do I get my hands on it? We'd like to just continue with a 4" ABS if possible.

If Fernco is our only option: 2 questions: The exterior of the CI is pretty chunky. Will that be an issue? And as this will be in about 2" of sand - salty sand - what is the likelihood of the stainless clamps failing? Stainless means nothing in Hawaii. It's only a matter of time.

Thoughts? Suggestions? Thanks!
Denise
 
You're talking about a 3.5 " c.o. fitting leaded into a 4" cast iron hub? Remove the fitting from the hub,
then insert 4" pipe with a "donut" (rubber bushing).
 
Aloha,
The clean out fitting will be 3.5" threads.
You may need to snap some pipe out and use a standard fitting instead.
And those will be installed with stainless no-hub couplings. I don't see too many other choices.
What is the OD (Outside Dimension) of the pipe that you have? Some 4" pipe can vary quite a bit when it comes to couplings.
 
Aloha all - I'll check the measurement tomorrow and even post some wonderfully sandy photos! We have a nice straight run of CI so the cut wouldn't be bad. We worry about the condition of the outside of the pipe taking to a rubber coupling. It's so corroded and uneven.

I clean a bit of it up tomorrow, take some measurements and post some photos for you all.

Thanks!

Denise
 
Terry said:
What is the OD (Outside Dimension) of the pipe that you have? Some 4" pipe can vary quite a bit when it comes to couplings.
Click to expand...

Looks to be about 4.25 OD or less-ish. We are going to cut it tomorrow so that I can get a better measurement.

Click for large view - Uploaded with Skitch
Click for large view - Uploaded with Skitch

And here is the whole picture! It's a roller coaster of CI!

Click for large view - Uploaded with Skitch

Based on the above, is this the best plan? Cut CI and use a Fernco? If we have 4" OD on the CI should I use the Fernco 3000-44 (that's the ProFlex one). Or the NH44 NO-Hub? It's seems like the No-hub is NOT stainless whiles the ProFlex is - and that is a concern with the salty sand.

And yes, we want to go with a 4" ABS is possible. We will continue to a Y reducer to 3" but continue a 4" new CO as it is at the end of our sewer line and we want to keep the wide access.

Mahalo!

Denise
 
Last edited by a moderator:
If it turns out to be 4-1/8"
then a copper size coupling on one end would work. I sometimes use a Mission copper by cast iron in those cases.
 
Hey Terry - Should we attempt to drill it out and use a Fernco donuts instead?

If not, I need help with the exact Fernco fitting as I will have to order it from the mainland. We are very limited in what we have here in Hawaii.

Pro-flex: I can do a 4" CI, Plastic or Steel to 4" Copper. 3001-44

http://www.fernco.com/plumbing/shielded-couplings/proflex-couplings

No-Hub is just 4", there is not option for copper. So that won't work.

So I should order the 3001-44, correct?

Mahalo!
 
Last edited by a moderator:
I don't buy my fittings at the home centers.
I would check out Pacific Plumbing Supply. They should have the "Mission" bands there in Hawaii, the same as they do here.

A safe way, would be to drill out the lead and use the hub that is there.

If you cut the pipe, then you would get an exact measurement for the pipe.
Copper DWV is 4-1/8"
New cast iron is 4-3/8"
PVC and ABS is 4-1/2"
Some old cast iron is also 4-1/8", but just because it's made from cast, doesn't mean that a coupling that is meant for a larger size will work on it. You have to buy size specific.
 
This is what happens when you have a father in law that is a semi-retired engineer with lots of tools!

IMG_2015.jpg

Little bit of silver solder, a drill and a lathe and taa-daa! We have our connection!

Thanks for the help!
Denise
 
It is not permitted to use a fitting that would restrict or reduce the I.D. of the pipe. If you are using 4" pipe, any downstream fittings must be 4"

To add to that, the 3 threads you have on that fitting are not likely to be adequate for properly tightening any threaded pipe fitting.
 
Do you know one reason those cleanout tees have a 3 1/2" tap in them? It is so no one could use them as a connection for a sewer extension or revision. It is not an approved "drain fitting" because the opening does not have any "directional sweep" to it.
 
hj said:
Do you know one reason those cleanout tees have a 3 1/2" tap in them? It is so no one could use them as a connection for a sewer extension or revision. It is not an approved "drain fitting" because the opening does not have any "directional sweep" to it.
Click to expand...

Well leave it to the retired engineer to find a "good way" to do it wrong. lol.
 
Don't we have to deal with "unretired" ones everday, those who design all the "improved" plumbing fixtures and faucets? One of the reps had a cartoon on his wall. It showed a guy outside the R&D door holding a whip. The guy who answered the door is saying, "We have a guy here who wants to talk to the engineer who designed part number 456B?. Or the one who wanted a 9/16" hole bored down through a 1/2" rod and wondered why all he got was a pile of shavings.
 
I deal with 3rd party building envelope consultants all the time. Sometimes I wonder if they understand gravity...
 
hj said:
quote; Sometimes I wonder if they understand gravity...

Only as it applies to their laboratories, where they have ideal conditions.
Click to expand...
Well ... us engineers may not understand gravity, but at least we can bite out nails if we want to :cool:
 
hmmm....ok...

I guess if the thing screws on and doesn't leak - that's no good?
And if it's a straight line? Directional sweep?

I guess I don't see how a Fernco 3.25 to 3.5 is any different other than it doesn't screw on? But I'm not a plumber! ;-)
 
Your device makes a "reduction in size". There is NO "3.25 to 3.5 Fernco", because there are no 3 1/2" pipes. The Fernco or "screw on" would not be the problem if it were the correct size, but the fitting it is connecting to IS the wrong one.
 
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