Internal cleaning of HYDRIM Backflow Preventer

January 15, 2026October 10, 2019 by Brian Skellie

Product Support

Description:

Internal cleaning of Backflow Preventer. This procedure applies to All HYDRIM® G4 WD units C61WD & M2 G4 for all markets except North America.

The HYDRIM C61w G4 is equipped with an air gap / anti-suction device to prevent
backflow of dirty water into the water supply. No other air gap device is necessary.

NOTE: When a cycle is started (P1, P2, P3) the air gap is filled four times before the circulation pump starts.

Referenced Parts

Backflow Preventer 01-113318S (C61WD) and 01-113853S (M2 G4).

Required Materials

The following additional materials are required for this step:

1x large syringe with tube (or sprayer bottle)
1x citric acid-based instrument neutralizer (for example, Dr. Weigert Neutralizer or distilled white vinegar)
A long flexible bottle brush may be helpful

Cleaning Procedure: Backflow Preventer/Air Gap

Remove the top cover from the HYDRIM unit and the left side panel (C61WD) or rear panel (M2 G4).
Fill a large syringe with 50ml neutralizer and then inject it through the opening on the Air Gap (Fig. 1).
Turn on the device and go into the technician menu: Technician menu / Diagnostic tools / Component test / Filling Draining (Fig. 2).
IMPORTANT: Start the filling process by pressing the “On” button. Once the unit reaches the position “E = On, F=On,” immediately press the “On” button again. This action will prevent the unit from activating the Air Gap pump and emptying the air gap.

WARNING: The device may still contain residues of dirty water. Be sure to drain them via the drain hose as described, and do not pump into the wash chamber by starting the Air Gap pump. Otherwise, these contaminants can enter the pump and damage it.

Leave the liquid to work for approximately 10 minutes. Tap gently on the side of the Backflow Preventer with the palm of your hand so that the agent spreads and the dirt dissolves.
Drain the liquid via the drain hose (at the bottom of the unit). Repeat the process with the filling from point 2 on, for further visible contamination (e.g., shadows, coverings, biofilm).
When no more contamination is visible, apply another 25ml neutralizer with the syringe and inject it into the air gap via the opening. Fill the Backflow Preventer again by going into the Technician Menu / Diagnostics Tools / Component Testing / Filling Draining. This time, do not press the “On” button again after reaching the F-switch position. This allows the Air Gap pump to start, which cleans and descales it as it empties the air gap of the solution. Repeat this step if necessary.