I want to fit a sussex flange to a standard hot water cylinder about 10 years old, normally there is a 1inch bsp tapping, this one has a male thread out of the top with a compression 28mm to 22 mm end feed reducer, held in place by a 28mm nut and olive, it does not have a male iron to copper fitting, the threaded bit looks to be screwed directly into the cylinder but if so how can it have a 28mm compression nut to the top if the part that enters the cylinder is 1 inch bsp?