Noggin,
Since you're going commercial, you're probably well down the road on your design, but this is a liquid detection circuit that I've used. The grounded foils on both sides of the detection foil reduce the sensitivity to external objects. For the electrodes, you could use brass tubing, available at hobby stores, as solder-able crimp ferrules. But that brings up two questions:
1. Will brass be OK in the environment where you are intending to use them them?
2. Can the electrodes be slipped down the tubing before it is connected to the water supply, or do they need to be attached to already installed tubing?
Ken