sink garbage disposal connections

[sm_jamieson]

I would like to fit a garbage disposal to my new sink. I know they are supposed to mince up fine enough to go into a drain. I will have a gulley outside the kitchen (useful for garden stuff), and I could connect sink/garbage to that, but is there any reason why I cannot have a small soil pipe stack terminating under the kitchen sink and connect sink/garbage to that, even though there is no toilet ? Would I need an air admittance valve ? It strikes me that having such a stack around would also be useful for future modifications. Cheers, Simon.

[Set Square]

I don't see why you shouldn't do it if you want to - after all, many kitchen sinks are connected to stacks rather than going directly into a gulley.

My sink and waste disposal unit both discharge into a horizontal manifold under the sink whose output is connected to a U-bend, and thence out through the wall to a gulley.

After having to deal with a number of blockages, I re-jigged the pipework to ensure that the waste disposal unit discharges into the manifold directly opposite the oulet - so as to have as straight a path as possible to the drain.