In article , Flat
Eric writes
Thanks very much for all your comments Fred, they were useful. I have
a few more questions in response
You're welcome, but I am winging it here, I have no experience of saniflo at
all, hence my initial reluctance to respond.

I think the only way to make a reliable connection is to use a boss. If
that is the case, then you need to make room to fit one, even if that
means hiring an SDS blaster to make room to fit one. You can make good
the render/brickwork after the even.
OK I'll have to have a good look to see whether this is feasible in
the space I have to work with - it's very tight.

you don't really want a right angle bend in the pipe
just before joining the stack
Why is that? I understand that bends in general should be swept bends
and not right angle, but what's the significance of proximity to the
stack exactly?
My thoughts were that if it is going to block then it will do so at the 90deg
bend and had also assumed that you would be taking it straight through
the wall just before you bent it into the stack. That would make for a join
near impossible to dismantle and assess for blockage. Best to make
potential problem areas accessible for service.

so maybe that means working from inside
the house & removing bricks until you can make a straight connection to
the stack.
This could be interesting - I have a fitted kitchen on the other side
of the wall! The soil stack may just coincide with the Dishwasher bay
though.
On reflection, this is probably a bit daft as it would blow any chance of
serviceability.

Also, why copper, it's not the normal way to do things so as
a result there won't be fittings to do the job. Suggest you do it in
waste pipe of the appropriate size and
I understand that using 22mm copper is the best way of plumbing
Saniflow waste (as it is more robust than solvent-weld plastic). I
don't think it's that uncommon, therefore I assumed that someone may
have come across the same problem
- joining 22mm copper to cast iron stack
Again not my area, but 22mm does seem very small, is this just a shower
type or a toilet? Also, I would have thought that plastic would have a
smoother interface at the joints, less risk of burrs/blockage aaaaand
serviceability again, a few non solvent joints in the plastic would let you
dismantle if required.

to make a copper to (40mm plastic) waste pipe joint
Are there fittings to join 22mm copper to say 40mm plastic waste?
You can get rubber reducers from 40mm to 21.5mm plastic (20mm
overflow pipe) that may suit, but I certainly wouldn't trust such a joint to
any kind of pressure. Perhaps if it was the joint at the stack then it would
be ok, so that would be boss, solvent adaptor to 40mm then 40/21.5
rubber reducer but def don't make it concealed anywhere

Again, hope that helps . . . . some
--
fred