Friend of ours needed to have a little extension with downstairs loo and
washing machine a couple of years ago, done with two separate saniflo's
(probably just about justifiably).

Just got called to look at a leak on the discharge side from the loo.
For those not familiar, you normally plumb these using solvent weld with
just one (strong) demountable joint to the unit. Plumber chose to insert
a universal compression elbow between the S/W (which, to be fair, was
secure) and the male outlet from the unit, with acrylic caulk filling
the clearance since the geometry didn't permit any "grip" on the rubber
seal.