I've seen it mentioned a few times that polarity doesn't matter when it comes to the Tsunami pumps. But after some research and testing polarity definitely matters to both the performance and longevity of the pumps.

Although the Tsunami will pump water regardless of polarity, if the wiring is reversed it will "reduce performance and can cause pump failure." If you want an easy test, pop out the motor cartridge and watch the impeller direction. The impeller shape is clearly directional and much more efficient when wired properly.

If you are reusing sprinkler valve wiring, it's not easy to tell which wires are positive and which are negative. So an easy test is to hook the motor cartridge directly to the battery terminals. Brown to positive, black to negative. I used a D cell battery and that worked too. Take note of the direction the impeller spins. Now hook it to the valve wiring and see if it's spinning the same way. If not, reverse your wires.

In summary: Brown = Positive, Black = Negative.

http://www.wholesalemarine.com/blog/...i-bilge-pumps/