The “No Water” Error in Xiaomi’s Robot Vacuum Cleaner: A Complete Diagnostic and Repair Guide

You started cleaning, and the robot vacuum cleaner Xiaomi (or Mi Robot Vacuum, Dreame, Viomi) suddenly stops with the message “No water” — even if the tank is filled to the top? This error occurs in models with wet cleaning function (Mi Robot Vacuum-Mop 2 Pro, Dreame D9, Viomi V3, etc.) and can be associated with both banal inattention and serious sensor breakdowns. In 80% of cases, the problem can be fixed on its own without going to the service center.

In this article, we will look at all possible causes of error, from trivial (incorrect installation of the tank) to technical (faulty contacts or control boards), you will learn how to reset the moping settings through the Mi Home app, check the water level sensor with a multimeter, and what to do if the robot “does not see” water after falling. And for owners of models with electronic control of water flow (for example, Xiaomi S7), we will give hidden commands to calibrate the system.

Warning: if your vacuum cleaner is warranty, do not disassemble the case unless absolutely necessary - this will cancel the warranty obligations. Start with the software methods (sections 2 and 3), and move to the "hardware" only if the software solutions did not help.

1. Checking the obvious: 5 user errors

Before you sin on machinery, eliminate the human factor. In 30 percent of cases, the "No water" error is due to improper operation.

Make sure the water tank is installed before clicking.|Check that the tank cover is tightly closed (a characteristic sound should be heard)|Remove the protective film from the sensor (if the vacuum cleaner is new)|Rinse the tank - lime plaque can block contacts|Try other water (distilled or boiled often solves the problem)-->

Pay special attention to the type of water. Many users pour tap water, unaware that Xiaomi recommends using distilled or filtered (with a hardness of no more than 3°dH). Mineral deposits eventually cover the water level sensor with a thin film, which stops working. If your vacuum cleaner has been in use for more than 6 months, try soaking the tank in vinegar solution (1:1 with water) for 30 minutes, then rinse.

Another common mistake is water overflows, and in the Mi Robot Vacuum-Mop P and Dreame W10, the maximum level is marked by risk on the tank, and if you pour it above it, the sensor can work like an empty tank, and the same thing happens when there is a low level: some robots require at least 100 ml of water to activate the moping.

⚠️ Note: If you use a detergent, make sure it is specifically for robot vacuum cleaners (e.g. Xiaomi Mi Robot Detergent). household shampoo or soap forms a foam that blocks sensors and leads to error.

2.Reset the moping settings via Mi Home

If mechanical checks didn’t work, try resetting the wet cleaning settings through the official app, a method that works for most Xiaomi/Dreame/Viomi models on firmware in 2022 and later.

Instructions:

1. Open Mi Home (or Dreame if you have a Dreame brand).
2. Select your robot vacuum cleaner → go to Settings → Cleaning settings → Wet cleaning.
3. Click Reset the moping settings (in some versions of the app, the item is called Calibration of the water sensor).
4. Confirm the action and wait for the robot to restart (it will take 1-2 minutes).
5. After restart, pour water and start a test cleaning.

If your application does not have a reset point, try an alternative method:

1. Hold the power button on the robot body for 10 seconds (until the beep).


2. Release and press again once - this will activate the hidden diagnostic mode.




3. In the cleaning menu in the application will appear a new item "Test sensors".

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Once the settings are reset, the robot can run the first 1-2 cleanings unstable, which is normal, the system takes time to recalibrate.

3. Cleaning and diagnostics of the water level sensor

The water level sensor is the most vulnerable part of the moping system, which is a pair of contacts (in budget models) or an ultrasonic sensor (in premium ones, for example, the Xiaomi S7 MaxV), and over time the contacts become oxidized and the ultrasonic sensor is clogged with plaque.

To clean the sensor:

1. Remove the water tank and remove the lid (usually it is attached to the latches).
2. Find a sensor – these are two metal pins at the bottom of the tank or a small round hole (for ultrasonic models).
3. Wipe the contacts with a cotton swab soaked in isopropyl alcohol (do not use water!).
4. For an ultrasonic sensor, use a toothpick to gently remove plaque from the hole.
5. Blow the tank with compressed air (you can use a canister to clean the equipment).

If cleaning does not help, check the multimeter sensor:

⚠️ Note: In models with ultrasonic sensor (Viomi) V3, Dreame Z10 Pro) self-substitution of the sensor often leads to error E12 (In this case, you will need firmware through STM32 CubeProgrammer.

4.Firmware problems and hidden commands

The “No water” error can occur after updating the firmware or resetting to factory settings. 2021–2022 Mi Robot Vacuum-Mop 2 Pro, Dreame D10 Plus), where in the firmware versions 3.5.8_0020 and 4.1.2_0034 It was a water sensor bug.

Check the software version:

1. In Mi Home go to Settings → About device → Firmware version.
2. If the version is older than 3.5.8 but younger than 4.2.0, an update is required.
3. For forced updates: 1. Connect the robot to Wi-Fi. 2. Enter the code in the application: *#580# (opens the hidden update menu). 3. Select "Manual Update" and download the latest firmware from the official website.

For Xiaomi S7 and S7 MaxV models with water sensor error after upgrading to 5.1.0, there is a special calibration command:

1. Hold the Home and Spot buttons for 5 seconds.


2. The robot will emit two signals -- release the buttons.




3. Enter the sequence: Spot → Pause → Spot → Home.




4. Wait for the audible confirmation (3 short signals).

5 Mechanical breakdowns: when you can not do without disassembly

If all previous methods have failed, the problem lies in the hardware, and here are the typical malfunctions and their signs:

• 🔌 Oxidation of board contacts: The robot periodically "loses" water during cleaning. Requires cleaning with alcohol or replacing the contact group.
• 💧 Cracks in the tank: Water seeps past the sensor, causing it to show an empty tank.Look at the tank in the light - cracks are often invisible.
• 🔧 Sensor attachment weakened: When you shake the robot, the error disappears? So the sensor moves away from the board.
• 🔋 Pump malfunction: In models with electronic flow control (Dreame) W10) The pump may be blocked due to debris.

To diagnose mechanical breakdowns, you need to disassemble a robot.

1. Turn the robot over and unscrew 4 screws on the bottom cover (you need a PH0 cross screwdriver).
2. Carefully remove the cover, starting from the back (there are latches).
3. Disconnect the plume of the water tank (the connector is usually blue).
4. Check the integrity of the wires and contacts on the board (look for darkening or green plaque).

⚠️ Attention: In Xiaomi models S7 And the newer water sensor board is located under a metal screen, and you need to unfurl 2 contacts to access it (you need a soldering iron at 30 watts). Without soldering experience, you better not risk it - a short circuit will disable the entire board.

Xiaomi (Mi Robot)|Dreame|Viomi|Ecovacs|Other-->

6. Alternative solutions: if nothing has worked

If the diagnosis and repairs are unsuccessful, consider these options:

• 🔄 Firmware rollback: For Dreame models D9 Xiaomi S6 You can return the old version of the software through ADB. Instructions: 4PDA.
• 🛠️ Sensor replacement: AliExpress sells original sensors (see model code, for example, HBF5618-001 For Mi Robot Vacuum-Mop 2). Cost from 500 before 1500 ₽.
• 🔧 Sensor bypass: For power users, you can seal the resistor 1 kOhm parallel to the sensor contacts to trick the system, which voids the warranty and can cause the pump to break!

If you decide to replace the sensor yourself, here is the compatibility table for popular models:

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For example, for the Dreame D9, there are two versions of the sensor: DMS-WS01 v1.0 (until 2022) and v2.0 (after).

7 Prevention: How to avoid future mistakes

To prevent the “No Water” error from reappearing, follow these rules:

• 💧 Use only distilled water (or boiled water if not distilled).
• 🧼 Wash the tank after each cleaning – this will prevent plaque formation.
• 🔋 Do not leave water in the tank for a long time (more than 24 hours) - this leads to corrosion of contacts.
• 📱 Update your firmware regularly, but don’t install beta versions.
• 🛑 Avoid falling robot – even from a height of 30 cm can shift the sensor.

For models with electronic water flow control (Xiaomi S7, Dreame W10), start calibration through the service menu every 3 months (the command *#636# in the Mi Home app).

FAQ: Frequent questions by the "No Water" error