I need to make a transition from 2" PVC drain to 2" CI drain, outside of the house, below ground about 4" deep.

I know Fernco used to make a Proflex shielded transition coupling with a metal shield and a neoprene sleeve, where the sleeve has one end for PVC and the other end that is slightly thicker for CI. The difference is small and I have used it before, but only in the vent portion inside walls since these couplings are not rated for below ground applications (according to Fernco). I went to the big box store and all they have are the Fernco "PlumbQuik" couplings, and they are to transition between same size CI/PL/ST to CI/PL/ST. So these sleeves have the same ID and doesn't account for the slight difference between CI and PL like they used to. May be it's too small a difference to worry about?

Anyone has a suggestion what brand/model shielded coupling is best to use? I looked through Fernco's web site looking for a shielded coupling specifically suited for 2" transition from CI to PL that is rated for buried underground and came up empty.

The only ones I found that may work are the standard/medium duty/heavy duty no hub coupling:

[www.fernco.com]

so I might use those. Which leads to my next question, if I do use a no-hub coupling to go from CI to PVC, should I or should I not use a no-hub adapter on the PVC side? I know I asked this before and the answer was no need to worry about using one unless local code requires it. Is this still the general opinion?

Fernco says these rubber couplings are rated for inground use: [www.fernco.com].

Note these are "unshielded" , meaning no stainless wrapper around the rubber, just 2 clamps. In my experience, CI is the same OD as PVC, copper has a smaller OD and requires a special coupling with one end smaller than the other.

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Not a plumber by trade but a fierce DIYer

sum , you are stressing over something very small.

how far away is the cast iron joint ?
dig to it and use a donut like this.

LI Guy, in the days of lead and oakum, cast iron pipe had no real standard OD. some was thicker and some was thinner.
it made no difference since the installation process was inserting the male end into a very much larger hub.
then oakum was packed into the space and molten lead was poured.
so in my experience some cast pipe is larger OD than PVC while some is smaller.

If the cast iron is thicker you could use a 4 clamp no hub coupling.



Edited 3 times.

I don't use those rubber couplings. They may be rated for horizontal connections but not vertical connections, I am not sure.

In previous projects the CI pipes I have seen were slightly smaller in OD then the same nominal size PVC. They used to make a special shielded coupling to account for the slight difference. Not anymore. They also make a PVC to CI no hub adapter for the same purpose. Copper is quite a bit smaller.

Packy, yes it is a very small difference.

I am not sure where the hub is, I am guessing another eight feet since I am two feet in.

I never had luck using rubber donuts. They are so stubborn last time I tried to use one I said all the curse words that exist and eventually gave up and cut the fitting off instead.

well, there is always oakum and lead wool.

Gotta put some liquid dish soap on the donut, it will slide in easily. Not sure what your objection is to the rubber couplings, that's what they are made for. If the joint seeps a little it's underground, it won't hurt anything, not like it's inside of a wall.

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Not a plumber by trade but a fierce DIYer

and molten lead?

"Gotta put some liquid dish soap on the donut, it will slide in easily."

Depends. A newer hub with a nice smooth round inside surface of the hub, may be. The few times I did this I was ways dealing with existing old hub underground so the inside of the hub had corroded buildup that needed to be cleaned with a wire brush. Then most times you are not in a perfect position to pull or push. So you are laying or in a squat position on the ground, where the pipe is horizontal and you are stretched fully down to apply the donut inside a trench may be 10" - 12" wide the most. So yes soap detergent, Vaseline, tried everything and I just had bad luck with them LOL.

Which is why I use the rubber couplings with the clamps....

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Not a plumber by trade but a fierce DIYer