Duofiller Core troubleshooting guide

Too much foam. Foaming might be tricky but there are a few rules of thumb that will greatly increase the success rate:

  • Make sure the beverage is cold, 4C or lower
  • Make sure the carbonation is finished. We recommend using force carbonation (sit and forget) at stable pressure/temperature for 9 days or more. If you quick carb or use a carb stone, shake the keg, roll the keg, etc; from experience, we recommend letting the beverage rest 4-7 days (at cold temperature) before filling. This is for the CO2 pressure to get completely in equilibrium with the beverage pressure.
  • Don't shake the keg during its stabilizing period.
  • Never decrease the keg pressure after carbonation is done / before filling. It might cause massive foam since CO2 bubbles will start to migrate out of the beverage. If pressure is decreased then repressurize and wait another day for it to stabilize again.
  • Rule of thumb, if carbonation level is below 2.7-2.9 volumes then normal fridge temperature is normally cold enough for filling. If more than 3 volumes CO2 you might have to cool below 4C and maybe close to zero degrees to have a successful fill session. Always disconnect CO2 if you cool below 4C, otherwise, you will increase carbonation as the temperature drops. Disconnect CO2 -> cool down -> wait one day -> reconnect CO2 (remember, keg pressure is lower because the beverage is colder) -> start filling.
  • Use the thinner beverage line (white color tube), it will have better foam-reducing properties than the thicker beverage line (natural color tube).
  • Rule of thumb; use the white beverage line for carbonation level above 2.7-2.9vol, and the natural color tube for carbonation level below 2.7-2.9vol

Together with carbonation level, temperature is the most important factor that affects foaming.

Too little foam. Cap on foam is desired to avoid oxygen contact with the beverage:

  • Make sure you are using the thickest beverage line (natural color tube)
  • Increase keg temperature. For example, take it out of the fridge and let it heat up before continuing.
  • Increase keg pressure to increase flow. It will produce more foam but it's not as efficient as increasing the temperature.

Users carbonate their beverage differently and it affects the foam cap. In general, we recommend always filling cold beer but it also might be that warmer than 4C (5-8C) will work best for your beverage type and carbonation level. For stouts and porters you might have to go warmer. Do your experiments over time. Start cold and let it heat up until you get that perfect foam cap, eventually go colder if there is too much foam at 4C

Beverage valve does not close / fill head dripping:

  • This happens if beverage pressure is too high. Lower beverage pressure to 20 psi / 1.4 bar or below.

Inconsistent fill level in "Can Mode":

  • Lower CO2 purge pressure. Max 3 psi / 0.2 bar. Slow purge without turbulence gives the best purge and saves you CO2. Too high purge pressure will disturb the level sensor and that will cause inconsistent fill level.
  • Calibrate the fill level with the actual beverage and actual flow rate.
  • The fill level will be less accurate with highly carbonated beverages like soft drinks and cocktails. Consider using bottle mode for filling when filling highly carbonated beverages.

The can is overflowing in "Can Mode":

  • Lower CO2 purge pressure. Max 3 psi / 0.2 bar.
  • Set the fill level lower. The sensor can not detect that the can is overflowing so it will continue to pour until it is manually stopped. Set a fill level that gives a small margin against overflowing, at least equal to the sensor's accuracy/repeatability (2%).

Inconsistent fill level in "Bottle Mode":

  • Check keg pressure / CO2 regulator. Stable keg pressure is the key to having a consistent fill level in Timer Mode. If you adjust the keg pressure then reprogram fill level or use correction value in the web interface. Make sure the beverage line is primed with liquid and that the can/bottle is empty before programming.

"Can Mode" fill level is not stored:

  • The sensor needs to register a liquid height of 25mm or more to store the fill level.

Red light on startup:

  • Failed to connect to wifi. Reset network settings and try again.

Tips and tricks

How to set CO2 purge pressure

The Duofiller requires low CO2 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 CO2 pressure will be dialed in perfectly:

  • Set the regulator to zero. Usually, that's done by turning the regulator screw anti-clockwise until the gas stops flowing
  • Push the Duofiller button to start a purge. LED is blue while the purge is ongoing.
  • While purging is ongoing increase regulator pressure until you hear CO2 starts flowing. That's it, the CO2 purge shall barely be hearable.

A slow and steady purge avoids turbulence and saves you CO2. There's no point in wasting CO2 by using high CO2 pressure as it's enough to purge one can volume. If done slowly the CO2 won't mix with the oxygen but slowly push it out from bottom to top.

Fine-tune fill level

To fine-tune the fill level you can use the correction value in the web interface. In can mode you can also move the CO2 purge tube up or down and the fill level will move correspondingly. This is because the fill level is measured by the pressure in the CO2 tube (pressure = liquid height above the CO2 tube tip) and if you move the tube up or down the liquid height that's measured by the CO2 tube will change.

Extending the beverage line

In general we don't recommend to change the line length. If you need to extend it for reach purposes, then we recommend to extend the 3/8" OD line between the keg connector and the Y-splitter. Important: do not create any restriction upstream the Y-splitter as that will cause foaming.

If the 3/16" OD lines (between the Y splitter and the Duofiller) are extended the flow rate will be reduced and also it might lead to increased foaming since the lines will pick up more heat from the ambient. If the purpose of extending the lines is to reduce foaming, then first investigate if possibly your beverage is over-carbonated, too warm or the carbonation is not completely finished.