There is no industry standard for Unions. The various brands have their own unique style, which means you must use the unions provided with our spa pump. This will most likely involve cutting off your old unions and installing the new ones (400-4060) shipped with the spa pump. If your heater is directly coupled to the spa wet end, then our pump will probably not work as the union will most likely be different. Be sure to look at the motor voltage, not the voltage supplied to the spa to determine the correct pump voltage. When removing power cord from existing pump we recommend you mark your wires for"common","High speed","low speed". The pump does not come with a power cord. The connection diagram for the new pump is located on the motor name plate. The wet ends can be rotated by simply loosening the motor thru bolts and turning the pump head, allowing the discharge to point to 3 O'clock, 9 O'clock or 6 O'clock. Not Self Priming-Water must be above pump head in order to operate properly. 1.5" refers to the size of your PVC plumbing supply lines. It has nothing to do with the size of the union nuts, the size of the threads on the wet end or the inside diamater of the inlet/outlet. The PVC pipe slides into the union and is glued with PVC cement. 1.5" plumbing means you have 1.5" schedule 40 PVC supply lines (1.5" I.D.; 1 7/8" O.D. on the line) circumference = 6.5" (wrap a tape measure around the pipe). If you are unsure if this pump will work for you, please call us, we can help assist you in your selection. If you only require a one speed pump, this pump will work fine. Simply just use the high speed connection. Optional debris basket 310-5400 available.