Fernco/No-Hub not sealing on cast iron

[Bcarlson78248]

I dug up my basement floor to access the existing 1940 4" cast iron drain pipe and add a new floor drain connection. I cut the CI pipe in two places and added in the connection for the new drain using 4" pvc and two No-Hub (metal banded) Fernco fittings for PVC to CI . However, on one side I am getting a drip from the fitting. This is the fitting I used (http://www.homedepot.com/p/Fernco-4-in-EPDM-Rubber-Coupling-P3005-44/100147217?keyword=p3005-44)

The old cast iron pipe had quite a bit of dirt/corrosion on the outside and I think the rubber collar and metal band are not making a good seal. I already tried to wire brush the outside of the pipe, but it still has some rough areas where the fitting slides over and the band clamps on. I can tighten up the bands some more, but want to get my torque wrench out first to make sure I don't get carried away and go well beyond the recommended 60 inch lbs.

Can I use some type of sealant between the rubber fitting and the cast iron pipe to allow for the roughness of the pipe? The rubber collar is already a tight fit on the pipe, so the no-hub fitting seems to be sized right.

Thanks,

Bruce

 

[Standardairconditioner]

Lumpy rusty surfaces can never make for a good contact. A lot of automotive bodywork DIY folks always try this, and then wonder why their Bondo falls off after a few weeks.

You want to get that surface as smooth as possible, the iron will be rather soft and should be easy to smooth out as you work you way down from heavy grit to something finer like 220 or 320, and then coat it off with some fast drying rustpaint.

Then you can use anything for a sealant, as the rubber coupling will do most of the work. Specific RTV gasket sealant will work, which is silicone anyways.

 

[Sponsor]

 

[Bcarlson78248]

I picked some additional sanding supplies today and will make another try at smoothing out the surface. The first time I used a wire brush and it had very little effect for smoothing the pipe. The pipe has been in the ground for 75 years, so what looks like surface dirt and corrosion is very firmly embedded in the iron. I also bought silicone RTV and after re-sanding the pipe I will reassemble this time with RTV.

Bruce

 

[Terry]

Check the outside dimension of the old cast. It may be 4-1/8" OD which would make it a copper size.
For those I use a copper by no-hub coupling.

 

[Standardairconditioner]

The (mechanical) wire brush is exactly what you use, and you gotta go at it for more than a few rounds. I usually end up destroying wire brushes when I do automotive restoration work. A lot of folks encounter your similiar problem when they try to change a brand new radiator hose over a rusty thermostat spout.

Rust is harder than metal, so do your best with the wire brush, and be sure to use a nice heavy high amp drill that will handle the continuous pressure. At this point try the Fernco and you'll watch how well it fits without even tightening the metal screw clamp.

Finish it with a wetsand of 220 or 320 grit wet paper, a quick one layer spray of Tremclad, and then bit of RTV in the Fernco's ring grooves.

 

[Bcarlson78248]

I used a wire stripping wheel and then sandpaper, and then added a bead of silicone RTV before I reassembled, and it looks likes it is sealed up completely on the cast iron pipe. I'm not sure I got 100% of the rust off, but it was smooth enough to let the clamp work and seal the rubber against the pipe.

I did learn one lesson about cleaning out the pipe by running clear water before you pull it apart. I had run quite a bit of water through before I originally cut the pipe, but during my retry I was in a hurry and only ran water for a short time. The smell was considerably worse this time, and the residue left in the pipe was more than just water . I will flush with lots of water before I cut a horizontal sewer pipe again.

Another question - What do I need to support this junction before we repour cement for the floor? I've see some articles that suggest pouring cement under the no-hub area for support, and others just use fill. The CI pipe I cut is fully embedded in the clay/dirt on both sides, so that is not moving. I just need to support the PVC wye that I added, and its connection to the new PVC drain pipe.

Thanks,

Bruce

 

[Standardairconditioner]

Well you surely don't want to make cement shoes out of your repair. If clay was there before, you'll put the clay back. If you were a client, I would put the clay back, then cement over the floor.

But if this were my home, the problem I have with cementing the floor back, is I'll always wonder how the repair will be in a few years. Can rubber last 10, 20, 30 years? I hate doubt, and doubt drives me nuts, especially when I can do something to eliminate doubt.

You might want to consider building a trap. That's a box made of cement, your repair is suspended in air, and once your box is done, it is just gravity covered with a metal plate, or a piece of 6mm plexi glass.

 

[Master Plumber Mark]

usually when I deal with a cast pipe and no hub fittings i like to use pvc glue on the pipe and inside the hub
you put it together and tighten it down and it makes a hell of a seal... within an hour it will not come apart again....
I would guess it will last a good 45 years...

 

[Standardairconditioner]

I'm just not crazy about burying soft plastic. Imho, majority of rubber couplers that are used, are not buried, and in visible repair areas.

I would contact the company (Fernco) and get it in writing that their couplers can indeed be buried.

Like I said, if it was for a client, I'd do it anyways, cement it up, and get paid.

 

[Bcarlson78248]

The Fernco documentation says these no-hub couplings are "tested for underground use", and if I am reading the local code correctly the banded no-hub coupling is also approved for underground use in my city.

Bruce

 

[CountryBumkin]

The (mechanical) wire brush is exactly what you use, and you gotta go at it for more than a few rounds.

No amount of grinding is going to fix that.