this is the email I got from curt at neptune
I recommend that you use a 3rd party product, the waterbug (part #WB-200)
for your water on the floor sensor. A search on goggle will find many
sources for this sensor.
Most connect the Waterbug (WB-200) to the IO breakout box we sell. You
need to have a 2 conductor wire to connect between the breakout box, and the
water bug. One wire will connect the C terminal of the water bug to the GND
terminal of the breakout box. Another wire connects between the NO terminal
of the water bug, and the I1 terminal of the break out box. I believe that
the water bug also needs power supply/AC adapter to be connected to the V+
and GND terminals (see WB-200 documentation for exact connections and AC
adapter type).
Curt