I like the sleeved ones, wouldn't use one without, but I just want to know the article in the code that says you can't use one, I know it must be something to do with not enough support or something. I can't find an article that says not to use rubber ferncos except below grade. Maybe the inspector can explain, I just want to know and he's in Pa where I live.
Go here
http://www.fernco.com/speccode.asp They have all the approvals and then check out their installation guides.
But this is where the great divide is.
As plumbers we are consistently working "outside the book" in reference to a million situations that present us in everyday work. You can't "go to the book" always.
Sometimes you have to truly think of the situation (ferncos) and think to yourself, "Is this an appropriate, non-fouling, error-free way of constructing a plumbing system?
If you've been a plumber for any amount of time, you'll see these in their use because they are the shortcut to transitioning pipe, cheaply.
When they have to hold pressure due to a backup, they expand and bulge. They also leak if there are points of movement in the connection from vibration or operation of the fixture it connects to.
Piping can instantly become misaligned in those fittings above ground. They're fine for underground because instant compaction provides the support for the fitting, with the understanding that the installer uses grillage to fill around the pipe.
There's nothing wrong with following the code book to a tee, but you'll eventually figure out that we as plumbers have to think outside that book to what we feel is in the best interest of industry and what provides the best repair.
If we outperform the code book, we've done our jobs as plumbers to protect the health of the nation. If we live by "well if it's not in the codebook, it must be okay" theory, then you don't understand the logic of how and why that book was created to begin with.....
It's an ongoing process of changes and revisions, certain products worked for a while until age changed that line of thinking, graduated to its removal or limited uses in the plumbing system that provides longevity without premature failure.
Yeah, something like that.