Lelit Bianca: Steam Boiler Fill Probe Inspection and Cleaning

A steam boiler that over-fills, fails to fill, or fills intermittently can be caused by faulty or dirty fill probe. Use this guide to inspect and clean your machine's fill probe.

Tools needed:
- 12mm and 19mm crescent wrench
- PTFE tape
- Coffee equipment cleaner (Urnex)
- Emory cloth or scouring pad

NOTE: The machine must be unplugged and cool to the touch before beginning.

If your fill probe has developed a leak at the base fitting, scroll down to the bottom of this article.

1. Remove the panels from the machine.

2. Identify the fill probe.

3. Disconnect the electrical lead from the fill probe.


4. Use the 12mm and 19mm wrenches together to unscrew the fill probe assembly from the boiler. Hold the bottom hex fitting firmly with the 19mm wrench while turning the fill probe retaining nut with the 12mm wrench.

NOTE: If you are resolving a leak at the base of the fill probe assembly, instead use only the 19mm wrench to unscrew the complete fill probe assembly from the boiler. Then scroll to bottom of this guide.

5. Inspect the fill probe assembly for debris or scaling. Even a small amount of build up on the fill probe tip can prevent the machine from accurately sensing the water level in the boiler.


6. Remove the fill probe from the retaining sleeve. Use a mild abrasive pad and coffee machine cleaner to thoroughly clean the fill probe.


7. Reassemble the fill probe assembly, taking care that the tip of the probe extends beyond the Teflon retaining sleeve.


8. Wrap the threads of the fill probe housing with PTFE tape before re-installing into the boiler. 

7. Use these instructions in reverse to re-install the fill probe into the boiler.

8. On the first start up after cleaning the fill probe the boiler will likely need to be purged, as it will still be over-full from the last time the machine was used. Don't skip this step!

To do this, start with the machine off and direct the hot water wand into a large pitcher, then fully open the hot water knob and power the machine on. As the machine reaches full temperature, water will begin to flow from the hot water wand. Wait for ~8-12 fl oz to be dispensed, then turn the hot water knob to the fully closed position and allow the machine to finish heating as normal.

NOTE: If your fill probe has developed a leak at the base fitting, it is best practice to remove the whole fill probe assembly from the boiler. Clean any thread sealant residue off of the boiler and fill probe threads, then wrap the threads with PTFE tape before re-installing.