How do I replace a disposable CO2 cartridge of a tap water cooler?

Is there little fizz on the water (sparkling water not good)? Is the pressure gauge lower than 3.5 bar? Time to replace the CO2 cartridge.
 

1. Unscrew the pressure gauge from the empty bottle
2. Bring the empty CO2 cartridge to the recycling park
3. Remove the seal from the new CO2 cartridge
4. Screw the pressure gauge onto the new cartridge until it is firmly tightened.
5. The pressure gauge is automatically back at 4 bar