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Over time, some malfunctions can occur in biogas during its use, and failing to address these issues promptly can affect its performance and cause losses for users. Leakage of water or gas is one of the common faults. As to how to detect such faults, based on the practical experience of technical personnel, the author has compiled the following four points for reference by colleagues: First, carefully inspect the inner wall of the biogas digester for any cracks or pores, and check whether the gas ducts are loose ； Tap various areas inside the tank with your finger or a small stick; if there is a hollow sound, it indicates that the coating is peeling. Also, check the pool walls for any signs of water leakage. For areas where seepage is not obvious, first clean the surface and sprinkle cement powder evenly over it, then apply a layer of cement paste. If wet spots or lines appear, they indicate leaks or cracks. II. Method of marking water level in the tank: Open the movable cover and fill the tank with water up to the lower edge of the cover. Once the tank walls have absorbed enough water, the water level in the tank will drop slightly; then fill it back to its original level. After 24 hours, if the water level does not drop, it indicates that there is no leakage in the biogas tank ； If the water level stops falling after reaching a certain point, mark that water level line; then look for cracks and pores above that line, and finally drain the water to carry out repairs. III. Using air pressure to check for leaks: After confirming through the aforementioned methods that the tank does not leak, scoop out some of the water from the tank so that the water level drops to 70–80 centimeters below the opening of the movable cover (the design zero-pressure level). Then cover the opening with the movable cover and seal it. Attach a tee to the gas supply pipe, with one end connected to a pressure gauge and the other end connected to an air pump or small compressor, in order to inflate air into the tank. When the water column on the pressure gauge rises to the designed pressure, stop inflating and turn off the switch. After 24 hours, if the water column on the pressure gauge drops by 3-4 centimeters, it indicates that there is a leak in the gas tank. IV. Checking for leaks using water pressure: Fill the tank with water to a level 70–80 centimeters below the opening of the movable cover, then close and seal the movable cover. In the case of a digester without an arch-shaped cover, the water level should be set at approximately 20 centimeters below the bottom of the feed inlet or 20 centimeters above the top of the discharge outlet. Next, connect a pressure gauge to the gas pipeline and continue filling the tank with water. When the water column on the pressure gauge rises to 40 centimeters, stop adding water and observe whether the water column on the gauge drops, in order to determine if there is a leak in the biogas digester. When checking for leaks in biogas digesters using air pressure or water pressure methods, after observing over a period of 24 hours, the gauge reading remains stable, or the change in pressure is within 2 centimeters, which indicates that the system is in good condition. When the water level drops by more than 2% but less than 20% within a day and night, it indicates that there is micro-perforation leakage in the gas chamber of the biogas digester. There are two reasons why a water column can remain stable once it has dropped to a certain height: one is micro-porosity leakage, as these micro-pores allow gas to escape under higher pressures, and they are unable to retain gas under lower pressures ； Secondly, there is a leak in a certain part of the inner wall of the gas tank; when the air pressure drops, the water level in the tank rises. The rising water level seals off the leaking area, reducing the volume of the gas tank and thus creating a water seal effect ； The continuous drop in the water column indicates severe air leakage in the air tank, which requires repair.