Here is the simple 2 microw switch method,the nice thing about this method is that the radio is isolated from the high power circuit.
Very reliable and cheap to make and repair.
LED indicators can be added to other locations to indicate flow direction or status of switches.
Never are 2 swiches in use at the same time due to the mechanical arm setup.
When making the switch use goop or equivalent lightly applied to the proper side of the switches insuring not to get the glue on the lever as this would jam the switch,clamp them in place so that there is enogh space for the arm to travel and straight across the servo.
Once dried connect to radio ,without the servo arm in place,[zero out] the servo or be sure the stick or knob is at center nuetral position.
Next instal the arm and move the servo via the radio and adjust the throws in both directions so that the servo arm does not over throw or under throw the switches,be sure your radio can do this ,or like on some radios adjust the servo throws from lock to lock with the switches wet with glue no pre drieing ,that way the servo or switches won't get damaged.
Once the above is done saulder up the connections and test the operation of the pump,to reverse the operation of the switch simply reverse the pump leads.
Be sure to use a filter on the pump.
A resetable fuse can be placed as shown.
Microw servos and sub microw switches make for a very compact and neat assembly and if a waterproof servo is used the switches still function in an emergency.
PM me if you want one.