... quote--
Bob La Londe
After reading the instructions I have not seen how the transmitter
battery can be replaced so I am assuming that it has a finite life. It
may use one of the ten year batteries like ITI uses in their alarm
transmitters. --quote--

Im sure I read that the battery in the little green thing (transmitter)
lasts like 400 hours. Its actuated by water, turns off out of water. You
dont replace the battery you buy a new transmitter costs like $20.
Ive been looking at this waiting for it to go on xmas sale well it never
did so most likely will get one come April.