Tennant T391 Manuel D'instructions page 15

Once collected in the dirty water tank, the converted water becomes plain
water again.
The ec-H2O NanoClean system can be used in all cleaning applications.
rate
button (Fig.6A), which is located on the ec-H2O NanoClean module:
one Led = low,
two Leds = medium (factory setting),
three Leds = high.
The ec-H2O NanoClean module is located above the head assembly.
6
6A
EN 15