On Wed, 11 Oct 2006 11:22:52 +0100, Stuart wrote:

Get a 22mm elbow and fit a reducer to 15mm in to one leg

That's the approach I've taken for similar fittings in the past. Also for
reducing T's. It's often cheaper to use a bog standard fitting + reducer
than to mess about with rarely used items. Also since the reduced fits
internally on the 22mm side it doesn't extend the fitting much. If length
really is an issue it's possible to shorten the reducer and one of the legs
of the elbow a few mm using a wheel cutter.