I hope I'm not interrupting the main thrust of this thread but I would suggest that in any case you use a double pole switch rather than the existing single pole switch. I'm thinking that your current switch is switching on and off only one of the two 220V lines. That might start and stop the motor but it's leaving the second line un-switched and therefor fully energized at the motor all the times. If someone thought the switch was shutting off electricity to the pump and started poking around, they would be in for a rude surprise.
If you let the two speed switch on the pump be the control for that function, then you can use a plain double pole switch (DPST) available at Lowes for about $13. That is different from a double pole-double throw switch (DPDT). The plain double pole switch is like a standard light switch, just ON and OFF positions. The double pole-double throw switch has three positions - OFF at the center position and ON at the up and the down positions.
Hope this doesn't complicate matters but I saw it as a possible point of confusion which hopefully I haven't made any more confusing!
Gregg