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Please fill water tank (full)

Display shows 'Please fill water tank.' despite the fact that the water tank is full — Water supply blockage or sensor issue

Siemens · EQ900 TQ900 Coffee Machines

What does Please fill water tank (full) mean?

The display prompts to fill the water tank, even though it is visibly full. This indicates a problem with the tank's seating, water quality, filter, or an internal sensor.

Common Causes

  • Water tank is wrongly inserted
  • Carbonated water is in the water tank
  • Float is stuck in the water tank
  • New water filter was not rinsed as per instructions
  • Air is trapped in the water filter
  • Water filter is old and needs replacement
  • Limescale deposits in the water tank are blocking the system

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Insert the water tank correctly and ensure it is seated firmly in place.

  2. 2

    Empty the water tank and refill it with fresh, still tap water; avoid using carbonated water.

  3. 3

    Remove the water tank and clean it thoroughly, ensuring the float moves freely.

  4. 4

    If a new water filter was inserted, rinse it according to the instructions and then place it into operation.

  5. 5

    If air is in the filter, immerse it in water with the opening upwards until no more bubbles appear, then reinsert it.

Browse all codes in this manual (27)
Verified technical data. Last updated: April 2026

Related Faults

Appliance unresponsiveAppliance no longer responds — Appliance has a faultBrewing unit jammedBrewing unit cannot be removed — Locking device jammedCoffee grounds wet/not compactCoffee grounds are not compact and are too wet — Grinding or bean issue
Source: Siemens EQ900 TQ900 Coffee Machines
Open Manual (Page 66)Search more codes in this manual