I installed the Spec. C sensor and activation switch on my USDM STI. Its been five months now with no issues at all. When I drive the car hard it uses nearly as much waster as gas. When I drive normally I can get several days on a tank of water. Come to think of it, I took the car to work today and burnt through the entire bottle of water in about 80 miles.
I could not imagine that the pump costs much more than the pumps that run the windshield washer bottle ($40-80 max). If it goes just put in a new one.