Notes: In order to avoid the breakage of the glass laser tube due to the heat generated during laser excitation, it is necessary to maintain the water-cooling effect with sufficient distilled water.

Maintenance Steps:

1. Remove the screw on the handle of the back lid and open the lid.
   
   
   

2. Unscrew the barb fitting and aim the laser head at it :

   a. Unscrew the barb fitting near the low-voltage side (near the reflective mirror) on the flow sensor >

   
   
   b. Place the flow sensor inside the water container > Lift up the water hose near the low-voltage side slightly to let some water flow out >
   
   
   c. Aim the air gun or other devices at the barb fitting opening. Be sure to ask someone to assist in holding the flow sensor above the water container to avoid spilling water after the air pump is activated
   
   
   
   
3. Connect the barb fitting back:
   Pre-turn the water hose by two turns to two and a half turns (the position of the hose clamp can be used as a reference) > Connect the barb fitting back to the flow sensor.
   
   
   
4. Use a double-head wrench to open the water pump cap:
   
   
   
5. Put in the funnel:
   
   
   
6. Restart the machine:
   Go to Touch Panel > Maintenance > Pump. The water in the tank will be pushed into the cooling system.
   
   
7. At the same time, gently fill in the cooling water with the funnel until the water tank is 80% full.
   
   
    Watch the water level carefully to prevent it from spilling over. Distilled water is strongly recommended.
   
   
8. Check the water level：
   Repeat step 7 few minutes until there is no big bubble in the hose and the water level of the tank no longer decreases.
   If the water pump does not work after pressing the button, please try squeezing or pinching the hose to let the air flow and allow the water to flow normally.
   
   
   
9. Please finger-tighten the pump cap in case of any damage to the tank.
   
   
   
   

10. Turn on the machine and run a flow test:
    Test flow speed: go to Touchscreen > Machine > Hardware setting > Test Flow Speed. 

    Normally, the result for the Beambox series should be at least 1L. 

    
    
    

Here is another video tutorial for water cooler Maintenance. 
Thanks for Mr. Dav Glass' Sharing.