# Tips and tricks

### How to set CO~2~ purge pressure
The Duofiller requires low CO~2~ pressure, max 3 psi/0.2 bar. Not all pressure regulator gauges have a scale range fine enough to be sure the pressure is below 3 psi. Follow this procedure and your CO~2~ pressure will be dialed in perfectly:

1. Set regulator to zero. Usually, that's done by turning the regulator screw anti clockwise until the gas stops flowing
2. Push the Duofiller button to start a purge. LED is blue while the purge is ongoing.
3. While purging ongoing increase regulator pressure until you hear CO~2~ starts flowing. That's it, CO~2~ purge shall barely be hearable. 

A slow and steady purge avoids turbulence and saves you CO~2~. There's no point in wasting CO~2~ by using high CO~2~ pressure as it's enough purge one can volume. If done slowly the CO~2~ won't mix with the oxygen but slowly push it out from bottom to top.

If you are unsure if the current purge pressure and duration is enough to purge your can or bottle volume you can use a plastic bag or balloon to measure the purge volume. 

### Fine-tune Sensor Mode fill level
To fine-tune the fill level in sensor mode you can simply move the CO~2~ tube up or down. If you move it for example 1mm up the fill level setpoint will move correspondingly. This is because the fill level is measured by the pressure (pressure = liquid height above the CO~2~ tube tip) in the CO~2~ tube and if you move the tube up or down the liquid height ithat's measured by the CO~2~ tube will change. Don't change the CO~2~ tube height unless you intend to change the fill level.