PVC shower drain to cast iron in concrete slab--use Fernco no-hub coupling? (photos)

[studio460]

Hi everyone!

I'm a do-it-yourselfer, but willing to hire a plumber. I just want to ensure it's done right. My main question is regarding the PVC drain connection to the 50-year-old 2" O.D. shower drain embedded in our "box-less" concrete slab (see photos below).

I'm guessing I have two options:

1. Jackhammer out a "box" around the existing drain to allow clearance to attach a Fernco no-hub coupling to the 2" cast iron drain in the slab, since the old cast iron reducer protrudes above the slab, by about one inch.
2. Leave the existing drain as is (with the protruding 3.5" cast iron reducer in place), and "build-up" the shower pan base, then connect the PVC drain to the 3.5" cast iron reducer using a Fernco no-hub coupling.

The problem with option two is, I don't know if that 50-year-old tar seal is good. Could I coat silicone (or other sealant) onto the existing interior of the cast iron reducer-to-cast iron drain connection? Isn't there some sort of sleeve-based solution for these types of installs?

Thanks in advance for any replies!

 

[mccmech]

Do I understand your project correctly, you are replacing a previous tile shower base with the Swanstone shower base shown in your pictures? If so, I would absolutely break up whatever flooring is needed and use a fernco to transition from the cast iron to whichever plastic pipe you plan to use. If you are installing a Swanstone base then the tar is a non-issue. All of the sealing will be done by the gromet which seals your base to the plastic pipe you stub up through the slab. If you are putting in another tile shower base then you have a whole other ball game. Please advise which install is being done.

 

[studio460]

mccmech:

Thank you very much for replying to my post! Yes, I've demo'd the old tile and hot-mopped shower base, and am replacing it with the following solid-surface shower pan:

However, the problem is the existing cast iron reducer that's attached to the 2" cast iron drain in the concrete slab by an unknown method which may or may not be still waterproof. Wouldn't I need to first remove the reducer, then demo the concrete around the 2" drain to allow enough clearance to fit the Fernco fitting around the 2" drain?

Secondly, is the Fernco no-hub coupler, in fact, the correct way to connect a 2" cast iron drain to a modern solid-surface shower pan?

Thanks again for any replies!

 

[LiQuId]

a Mj ( no hub coupling ) is the only good way to connect cast iron to Pvc or such.

I would break up the cementy in the area as you lifkely dont have room fort the shower pan to sit on top of the cast iron ( do you ? ) Regardless you will need access on one side to tighten the Clamps on the mj .

to me this pipe ( the cast iron ) looks to be a 3" if you say it has been reduced and there isa a flange at its bast then perhaps they just attached the 2" to the 3" with back to back flanges.

 

[studio460]

LiQuId:

Thanks for your reply! Also, thanks for confirming that the Fernco coupling (Mj?) is the best way to connect cast iron to PVC. I just thought there might be a more "permanent," sleeved or "welded" application available, since this all of this is going to be back-filled with the mortar bed for the new fiberglass pan.

Although I could sit the pan on top of the protruding reducer, I don't know if the reducer-to-drain connection is water-tight (the pre-existing hot-mop/tile pan was severely compromised, leaking to the foundation in multiple areas).

The reducer appears to mate directly to the 2" drain, sandwiched by tar--I can't see a flange. The 3" exposed cast iron part is where the old drain cover attached--there's even cast screw holes inside the diameter of the fitting for it. The drain definitely reduces to 2" about an inch below the part.

So, I suppose I have to jackhammer the concrete around the 2" pipe below, right? I believe the Fernco fitting has a hex-flathead screwdrive to tighten the bands, so at least I can use a socket-driver instead of demoing enough concrete to have enough clearance to get a screwdriver in at a 90-degree angle.

Thanks again for everyone's help!

 

[phishfood]

There is a no hub coupling made that is designed specifically for transitioning between cast iron and plastic piping. The outer diameter of cast iron is slightly smaller than that of the plastic, and the neoprene sleeve of this transition band has a different internal diameter on each end to allow for this.

Just to be clear, you will need to adapt to a short section of 2" PVC or ABS pipe, then seal the drain from the shower to that pipe.

 

[studio460]

phishfood:

Thanks for your reply! I'm going to caliper the O.D. of the cast iron drain to make sure. Just to be clear, here's how I understand the recommended procedure so far:

1. Jackhammer concrete foundation around the embedded 2" cast iron drain, to reveal a one- to one-and-a-half inch "stub."
2. Saw off the old 3" cast iron reducer.
3. Attach Fernco coupling to 2" drain, and secure with a socket-driver.
4. Attach other end of Fernco coupling to 2" PVC.
5. Set fiberglass shower pan in place.

Here's the part I'm fuzzy on now.

What parts do I need to mate the drain cover to the Ferco'd PVC? Do I attach the drain cover to a 2" PVC drain with some kind of screw-on collar (plus, apply silicone or plumber's putty under the drain lip?), then cement to the 2" PVC part that's Fernco'd to the cast iron drain? Or, do I somehow connect this more directly?

 

[LiQuId]

1. yes

2. use a grinder to cut a saw will take forever. wear appropriate safety.

3. yes, you will need a 5/16 socket driver.

this is where it can be tricky, and may vary depending on that particular shower pan. is the stubbed down peice 2" ? it should come with installation instructions.

almost all shower drains I;ve worked on use an assembled drain ( drain goes onto shower pan before tray is placed ) that you would then ( in this case ) glue a stub 2" piece onto. So I cannot say specifically what your next step is but....

If the sower pans fixture outlet pipe is integrated ( built into the tray ) then you would connect this direct to the mj as well, you would have to line the drain and the pipe up and then drop the tray onto it, you would then tighten the gear clamps.


not that its a concern for you either way but just to clarify for you a fernco has no metal collar on it an Mj ( stands for mechanical joint ) has a metal collar on it... they are pretty much the same thing but a fernco is not accepted for underground use.

 

[LiQuId]

having viewed the pictures it appears that the drain grate fitting is a push type fitting and the 2" pipe will press into the middle section, I have only replaced these types of drains cause they leaked. perhaps others have some installation tips.

I am a solid hater of pressure gaskets.

heres a link to the install pdf.

http://www.swanstone.com/images/link_installation/Shower Floors 06-10-10.pdf

its all in there.

 

[studio460]

LiQuId:

Thank you again, for your continued assistance! Okay, I re-read the installation instructions, and they make more sense now (clearly, I'm unfamiliar with most of this--I work in TV, and know virtually nothing about plumbing).

According to the Swanstone installation guide:

1. Demo a 6"-diameter cavity in the concrete foundation.
2. Cut the 2" cast-iron drain, 1/4" below floor.
3. Place pan and insert pressure gasket.

So, I gather, I don't really need the Fernco, since the supplied pressure gasket is designed to attach directly to 2" cast iron or PVC, according to Swanstone.

I am a solid hater of pressure gaskets.

However, as you mention, this never seemed to be the most robust installation to me either. But, do you agree that siliconing the holy crop beneath, between, and around the pressure gasket, and the fiberglass drain cavity, should do it? I mean, isn't the upside of the recommended installation, that, in case of any compromise in the seal, I can always just pull the pressure gasket (working from the top of the pan intact, and not having to destroy it), and simply install a new pressure gasket, with fresh silicone, at anytime?

Thanks, again, for your help!

 

[johnjh2o]

You can always do it the old way by calking the joint with oakum and pouring a lead joint.

John

 

[LiQuId]

lol, that way would be solid for sure...

You could sillicone around the pressure gasket ( between the gasket and shower pan, and also between the gasket and pipe ) though if installed correctlly this SHOULD not leak. make sure whatever you do that the 2" pipe does not sit higher that the top of the pressure gasket or water will pool there and be forced to rise before properly draining.

It looks like this pressure gasket is the only way to "properly" install the drain body though.

Sorry i've not much experience with installing these, as I said, I have only replaced these with new gaskets and only a few times as in my area these are seldom seen .

 

[studio460]

You can always do it the old way by calking the joint with oakum and pouring a lead joint.

John

Thanks for your reply, John. That's clearly beyond my skill level, but at least I can use that information to vet any furture plumber hires. Thanks again!

 

[studio460]

lol, that way would be solid for sure...

You could sillicone around the pressure gasket ( between the gasket and shower pan, and also between the gasket and pipe ) though if installed correctlly this SHOULD not leak. make sure whatever you do that the 2" pipe does not sit higher that the top of the pressure gasket or water will pool there and be forced to rise before properly draining.

It looks like this pressure gasket is the only way to "properly" install the drain body though.

Sorry i've not much experience with installing these, as I said, I have only replaced these with new gaskets and only a few times as in my area these are seldom seen .

Thanks for your reply, LiQuId! I think that's the plan, then, now that I more clearly understand the manufacturer's recommended installation procedure. I like that with this install method, it's easily re-done at any later date without having to pull up the pan. Thanks again for all your help!

 

[studio460]

You can always do it the old way by calking the joint with oakum and pouring a lead joint.

John

New problem!

Upon further review, I think that's the best solution, since I've now discovered a new problem: the 3" reducer mates with the 2" cast iron drain more than the 1/4" depth below the floor as recommended by the Swanstone installation guide. The end of the 2" drain stops about 1" below the floor, so it's too short to reach through the drain cavity of the new Swanstone fiberglass shower pan to enable the installation of the supplied pressure gasket with silicone. Here's what I think is next:

1. Jackhammer to a 2" (or more) depth, around the drain.
2. Laying in an oakum/lead joint to a short 2" cast iron extension (or other recommended material) to the required 1/4"-below-floor height.
3. Install rubber pressure gasket with silicone as directed by the manufacturer:

Will post new pictures, illustrating the "new problem" in a few minutes.

Thanks again for your help!

 

[studio460]

Actually, I think this would be easier:

1. Lay in an oakum/lead interior joint to the existing cast iron reducer to the 2" cast iron drain, just to ensure a water-tight seal remains in the 50-year-old, flange, and tar-attached joint.
2. File off the cast screw holes on the interior diameter of the 3" cast iron reducer to make a perfectly circular cavity.
3. Insert some dimension of cast iron or PVC which reduces to the 2" dimension on the top, and fit pressure gasket as directed in the Swanstone installation instructions:

[By the way, I'm calling area plumbers now for quotes on oakum/lead joint work, plus laying the mortar bed for the shower pan. It's clearly beyond my skill level, plus I'll be contributing to the local trade. So, rest assured, all of your collective, expert advice still helps your fellow tradesmen get work!]

 

[LiQuId]

Sounds like you should get a plumber to do this, it would make life easyer for you and ensure the work is done correctlly. not sure you should be requesting lead poured joints as much as just having one of them come out and give you a quote, there are several ways to accomplish this job finished and it would be up the the plumber you hire to asess the best way to acomplish that.

 

[johnjh2o]

If you feel you don't have the tools or the skills to pour a lead joint you could use oakum and lead wool in place of the poured lead.

John

 

[LiQuId]

isnt there another product also ?? pc-40 ( i beleive its called ) thats lead free? We dont do lead where i am as its prohibited even in drainage due to the water contamination.

I have poured 1 lead joint in my life THB, and Am surely not an expert at this. usually we woud open the floor and Mj, and then use cement to fill after.

We only use lead in the form of 40/40 solder on occasion on heating pipes.

 

[studio460]

Don't worry, I am absolutely hiring a professional to do this. I just wanted to hear everyone's advice so I can make sure it's done right--this basically has to last until I die, since I'm never moving or selling. The photos crashed my image editor--will post them soon I can recover them. Thanks for everyone's comments!