Reasons RV Grey Water Tank Is Reading Full When Empty

Recreational Vehicles (RVs) provide an exciting way to travel and experience the world without sacrificing the comforts of home. However, like any complex system, RVs can encounter issues that require troubleshooting. One such prevalent problem faced by RV owners is the grey water tank reading as full even when it’s empty. This can lead to inconvenience and frustration during travels. In this comprehensive article, we will explore in detail the seven common reasons behind this issue and provide effective solutions to address each problem.

Problem #1: Sensor Malfunction

The grey water tank is equipped with sensors responsible for detecting the level of liquid inside. A sensor malfunction occurs when these sensors provide inaccurate readings, leading to the tank displaying a full reading despite being empty. This issue can be particularly bothersome, as it deprives RV owners of an accurate assessment of their tank’s capacity.


  • Sensor buildup: Over time, the sensors inside the grey water tank may accumulate residue, grease, or debris. This buildup can interfere with accurate readings as the sensors are unable to detect the actual water level.
  • Electrical issues: Damaged wires or poor connections within the sensor system can disrupt the signals sent by the sensors to the monitoring unit, resulting in incorrect readings.
  • Sensor calibration: In some cases, the sensors may not be properly calibrated during the manufacturing process, leading to inaccuracies in the readings they provide.


  • Sensor cleaning: Regularly cleaning the sensors is essential to prevent residue and debris buildup. Use a recommended cleaning solution or a mixture of white vinegar and water to gently clean the sensors, ensuring they remain free of any obstructions.
  • Check wiring: Inspect the wiring and connections associated with the sensor system. If any damage or corrosion is found, repair or replace the affected components to restore proper functionality.
  • Recalibration: If the sensors are not calibrated correctly, refer to the manufacturer’s instructions to recalibrate them accurately. This process should be conducted carefully to ensure precise readings.

Problem #2: Tank Shape and Design

The design and shape of the grey water tank play a vital role in the accuracy of sensor readings. Irregular tank shapes or improper sensor placement can lead to false readings, confusing RV owners about the actual level of the grey water tank.


  • Odd tank geometry: Some RVs have grey water tanks with irregular shapes or internal partitions. Such designs can create false readings as the sensors may struggle to measure the water level accurately in complex tank configurations.
  • Sensor placement: In some cases, the sensors may be placed in areas of the tank where water flow is limited. As a result, the readings may not represent the overall water level accurately.


  • Tank replacement: In extreme cases where the tank’s design significantly affects the sensor readings, consider replacing the existing tank with a better-designed one that offers more accurate readings and simplified geometry.
  • Relocating sensors: Consult an experienced RV professional to determine if moving the sensors to a different location within the tank can enhance accuracy. Repositioning the sensors strategically can result in more reliable readings.

Problem #3: Residual Grease and Soap Scum

The presence of grease, soap scum, and residue from cleaning agents can create a coating on the tank walls over time. This coating can interfere with sensor accuracy and lead to the grey water tank reading as full when it’s actually empty.


  • Improper cleaning: If the grey water tank is not cleaned thoroughly after each use, residues from cooking grease, soap, and hygiene products can accumulate on the tank’s interior surface, causing a film that disrupts sensor accuracy.
  • Low-quality cleaning agents: Some cleaning agents used in RV grey water tanks may leave behind a film or scum on the tank walls, exacerbating the problem.


  • Thorough cleaning: After emptying the grey water tank, rinse it thoroughly with hot water to dislodge any residue. Use an approved tank cleaning agent specifically designed to dissolve grease and soap scum effectively.
  • Use high-quality cleaners: Select high-quality cleaning agents explicitly manufactured for RV grey water tanks. These products are designed to break down and remove residues without leaving any harmful films behind.

Problem #4: Debris and Solid Waste Accumulation

Solid waste and debris can accumulate at the bottom of the grey water tank, leading to inaccurate sensor readings. This build-up not only hinders the tank’s capacity but can also create unpleasant odors inside the RV.


  • Food particles: Improperly disposing of food particles and other solids down the drain can lead to their settlement at the bottom of the grey water tank over time.
  • Foreign objects: Accidental entry of non-dissolvable items, such as wet wipes or feminine hygiene products, into the grey water tank can cause obstructions and hinder the tank’s accurate measurement.


  • Proper waste disposal: Educate all RV occupants about the importance of proper waste disposal. Ensure that food waste is adequately ground and disposed of through appropriate means, such as designated trash bins or composting.
  • Use strainers: Install strainers on the drains connected to the grey water tank. These strainers will help catch large foreign objects, preventing them from entering the tank and causing clogs.

Problem #5: Tank Ventilation Issues

Inadequate ventilation within the grey water tank can lead to pressure imbalances, resulting in false sensor readings. This issue may also contribute to the formation of odorous gases inside the tank.


  • Blocked vent pipes: Over time, vent pipes connected to the grey water tank may become clogged with debris, dirt, or insects. These blockages restrict airflow and lead to pressure irregularities within the tank.
  • Faulty vent valve: The vent valve, responsible for allowing air to flow in and out of the tank, can malfunction or get stuck, affecting proper ventilation.


  • Regular maintenance: Routinely inspect and clean vent pipes to ensure they are free from blockages. Remove any debris or obstructions that could hinder proper airflow.
  • Check vent valve: Periodically examine the vent valve to ensure it operates smoothly and opens and closes correctly. If there are any issues, consider replacing the valve to restore proper ventilation.

Problem #6: Faulty Sensor Wiring or Circuitry

Issues with the sensor wiring or circuitry can disrupt the communication between the sensors and the monitoring system, leading to erroneous readings and inaccurate tank level displays.


  • Corroded wires: The sensor wiring may be exposed to moisture or harsh environmental conditions, causing corrosion over time. Corroded wires can disrupt the electrical signals between the sensors and the monitoring unit.
  • Frayed or damaged wires: Physical wear and tear, especially in the undercarriage of the RV, can cause sensor wires to fray or break, hindering their ability to transmit data effectively.


  • Wire inspection: Routinely inspect the sensor wiring for signs of damage or corrosion. If any issues are found, take appropriate action, such as repairing or replacing the affected wires, to ensure a seamless connection.
  • Protect wiring: To prevent future issues, consider using wire sleeves or conduit to shield the sensor wires from environmental elements that could lead to damage or corrosion.

Problem #7: Electronic Control Unit (ECU) Malfunction

The Electronic Control Unit (ECU) is responsible for processing the sensor data and displaying accurate tank levels. A malfunctioning ECU can disrupt this process, resulting in the display of false readings.


  • Electrical issues: Power surges, fluctuations, or other electrical malfunctions can damage the ECU’s internal components, affecting its ability to process sensor data accurately.
  • Software glitches: As with any electronic device, the ECU’s software may experience bugs or errors, leading to inaccurate data processing and incorrect readings.


  • Professional inspection: If there are signs of ECU malfunction or if other troubleshooting efforts have failed, it’s essential to seek the expertise of an RV technician. A qualified professional can diagnose and repair ECU-related issues effectively.
  • Software updates: If the ECU is programmable or has software that can be updated, check with the manufacturer for any available software updates. Installing the latest software version may resolve any software-related glitches and improve sensor data processing.


Experiencing a full grey water tank reading when it’s actually empty can be a frustrating challenge for RV owners. However, by understanding the common reasons behind this issue and implementing the suggested solutions, travelers can ensure their grey water tank functions optimally.

Regular maintenance, proper cleaning, and occasional professional inspections will contribute to a trouble-free and enjoyable RV journey, allowing adventurers to focus on the breathtaking experiences that lie ahead. Keeping the grey water tank in excellent condition not only ensures accurate readings but also helps maintain a hygienic and comfortable environment during your RV travels.

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