A no-hub connector should work. Keep in mind that PVC is normally not rated for pressure and the no-hub is a drainage fitting, not a pressure one, but it should handle some. Some pvc pipe that are rated for pressure, but it is not supposed to be used for hot water. What is the highest temperature of the water outlet of the heater? This could be a major problem, regardless of how you connect the two.
Another possibilty might be something like a Sharkbite, but I don't think they come that large (I think 1" is the largest). You could glue male threaded adapters on each end, then screw that into a threaded coupling, but you'd need to be able to separate the ends enough to get those in, glue one end, thread both adapters in place, then glue them to their respective bits. You could do the same thing except use a union to connect each side - that would require less separate to get the pieces in.