Well you want a switch to change the pump direction. This could be a boolean or an enumeration switch. You can edit the text on the switch to indicate the pump direction. Wire the control to either a case structure or a 'select' node, and in the case for 'pump reverse' wire the pump rate through a 'negate' node. So to restate that in short, you negate (make negative) your pump rate to reverse the flow.
