A maintenance indicator positioned on top
of the filter indicates when service is due.
The filter should be backwashed every two
months at the latest. Servicing the Duo DFR
requires no special tools. To service the
filter, open the ball valve and turn the lower
part of the filter 2 to 3 times to the left or
to right. Close the ball valve again. Even
during backwashing, the device continues
to supply filtered water into the potable
water system.