[waterfilters]

The system takes the battery so the indicator light is powered. You
will know when to change the filter based on the indicator light on
the faucet.
The battery goes behind the faucet; there is a lip there with a
battery insert. Putting the battery there powers the indicator light
on the faucet. There is a new version of the manual that includes the
instructions on the use and installation of the battery, the original
version of the instructions (the one that was sent with the unit) does
not state this and therefore a revision was necessary to get the
information put in the manual.

Thank you,
WaterFilters.NET