Cast Iron Hub to PVC Fernco rubber donut

[graym0nd]

So I have removed my existing cast iron main stack as I am remodeling our older house. I am replacing the main stack with PVC. I bought a 4" Fernco rubber donut that slides right into the hub. Is this how it is suppose to fit or should it be going over the top of the hub which is 6 inches across and 5 inch diameter inside?

If this is correct, then I don't see how it is possible to push a 4 inch pvc pipe into the inside hole as I have tried grinding the edges of the 4 inch pipe and everytime I try, the fernco rubber donut goes down further into the cast iron pipe and then I have to pull it back out and start over.

Any info, tips or suggestions would be much appreciated!

 

[wwhitney]

So I have removed my existing cast iron main stack as I am remodeling our older house. I am replacing the main stack with PVC. I bought a 4" Fernco rubber donut that slides right into the hub.

My understanding, which is not from hands-on experience, is that it should be a pretty tight fit. So if it "slides right in" the OD of your donut may be too small. On the other hand, it may be the right OD once the donut is expanded slightly by going over the PVC pipe.

Anyway, try putting the donut on your PVC pipe first, then slide the pipe/donut assembly into the hub. It should go together with some difficulty. Others here have more direct experience and may have more suggestions.

Cheers, Wayne

 

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[graym0nd]

Yeah...I tried that too but when I put the donut on the pvc pipe first and try to put it in the cast iron hub, the rubber donut slides further up the pvc pipe and never goes into the hub. Very frustrating.

Maybe the fernco I got is not the right one which is what I keep asking myself. It slides in the hub fairly easy with no issue. Not a tight fit although it touches all the way around. I didn't have to warm it up or nothing...took it out of the bag and slid right into the cast iron pipe.

 

[Reach4]

Donuts | Fernco - US

Fernco Donuts Sewer pipe compression joint sealers With the most comprehensive line-up of compression joint sealers, Fernco Donuts are known for creating a strong and lasting joint.

www.fernco.com

Fernco Donut Installation | Fernco - US

www.fernco.com

You are going to want to measure the hub accurately, phone Fernco, and get the right size.

 

[graym0nd]

Donuts | Fernco - US

Fernco Donuts Sewer pipe compression joint sealers With the most comprehensive line-up of compression joint sealers, Fernco Donuts are known for creating a strong and lasting joint.

www.fernco.com

Fernco Donut Installation | Fernco - US

www.fernco.com

You are going to want to measure the hub accurately, phone Fernco, and get the right size.

I also think that is the issue...the size may not be correct even though it seems to fit

 

[wwhitney]

Yeah...I tried that too but when I put the donut on the pvc pipe first and try to put it in the cast iron hub, the rubber donut slides further up the pvc pipe and never goes into the hub. Very frustrating.

Again, my comments are based only on reading here, and not first hand experience, but:

If I understand correctly, you put the donut in the hub, it goes in easily, but if you try to insert the pipe, the ID of the donut seems too small, so you end up pushing the donut downward. Conversely, if you put the donut on the pipe first, it will stretch over the pipe, but now the OD seems too large and you can't get it into the hub.

I think those conditions are in fact consistent with the correct sized donut. The point is that in the final configuration, the donut should be somewhat compressed, so that it pushes against the hub and the pipe to seal against them. Thus in the act of installing the donut, you have to compress the donut, and that makes installation somewhat difficult.

So what you may have to do is put the donut on the pipe, suspend the pipe in the hub close to its final location, slide the donut down to the hub, and then use a long 2x4 on end to hammer the donut into place in the hub. Lubricating the donut first, so that it is more likely to slide than catch and tear.

Cheers, Wayne