On Thursday, January 14, 2016 at 4:11:05 PM UTC-5, TimR wrote:
Water lines are under pressure, about 45 psig in my area. They're designed that way.

Waste lines drain through gravity. Most of the time there's no pressure at all on them, except when draining, and that's brief and minimal. They aren't necessarily designed to resist pressure.

I'd be cautious of any pressure technique.

Would a fernco hold 45 psig? On a 3 inch drain line? Maybe but I wouldn't risk it.

Fernco No-Hubs, even the heavy duty kind, are pressure tested
to a max of 4.3 PSI. Yes, I said four *point* three.

Last line of the Specifications section:

https://www.fernco.com/plumbing/shie...-hub-couplings