This pump is energy efficient and costs only pennies per day to operate. Its absolutely quiet, almost silent operation will assure your customer`s satisfaction. The newer pump has been completely redesigned with an ingenious rotating volute allowing installation in all plumbing configurations. Grundfos makes only this pump for the spa industry. It has a 1" barbed fitting which most Sundance used a glue in or 3/4" barbed fitting. You must adapt the plumbing to work on the spa or if your spa used a 3/4" barbed. you can use the 6500-460, E10-NSHN1W-19 Laing Pump, but would need to change positon of the base of the pump to adapt the plumbing. There is no straight across exchange out for the old pump.