See attached pictures. I'm having trouble tightening up the connections at my vulcan heater tube. The pipes are 1 1/2". The pump side has a pvc elbow which really needs a union there but I have no room. The elbow threads into a pvc male coupling which seems to be cemented into the metal heater. The filter side doesn't tighten up too well either. What is the proper connection to the threaded vulcan heater pipe?