Should a Fernco donut bottom out, or stay flush with top?

[ShelzMike]

Working on a 4" cast iron to 4" PVC junction. I used a wire brush on a drill and got the inside of the CI bell nice and clean, shiny even.

I contacted Fernco with my measurements and have the correct donut according to them. I put the donut in and when it is flush with the top of the CI bell, there is still about 1/2" maybe until the donut is bottomed out. Should it be bottomed out or stay flush. If I were to guess, id bet I won't have a choice and that when i put the PVC in, the acts of getting it in there will bottom the donut out anyway. Just wanted to be sure. Thanks!

 

[Terry]

If the pipe is snug, that it should be good. It's all about the seal.

 

[Sponsor]

 

[Reach4]

when i put the PVC in, the acts of getting it in there will bottom the donut out anyway.

When you install, you will lubricate the rubber with a liquid dish soap solution. That may affect how far you can push.

 

[Jadnashua]

FWIW, while there's a standard for the ID of the main body of the pipe, there isn't on the hub, thus, that's why there are lots of choices for the ID of the hub. It will probably move in some when you install the pipe into the donut...don't worry about it.