What is the reason why a self-priming pump cannot extract water?

The inability of a self-priming pump to suck water is usually caused by the following reasons, which require targeted investigation and resolution:

1. Installation and sealing issues

Pipeline leakage (accounting for more than 60%):

The deformation of the flange gasket of the inlet pipe, loose joints, or cracks in the pipeline can cause air infiltration and damage the negative pressure environment.

Detection method: Run the pump for 4-5 minutes and listen for a "hissing" sound close to the pipeline, or apply soapy water to observe bubbles.

Exceeding suction limit:

The vertical distance of the water source is greater than 8 meters (conventional pump limit) or the horizontal pipe is too long (recommended ≤ 10 meters).

Solution: Shorten the pipeline or replace the high suction pump (vacuum assisted suction can reach up to 30 meters).

Check valve failure:

The outlet is not equipped with a check valve or the valve plate is damaged. After stopping the pump, the liquid flows back and is sucked into the air.

2. Operation and maintenance issues

Unprepared water intake:

After the first start-up or long-term shutdown, the pump chamber is not filled with water, and the gas-liquid mixing cycle cannot be started.

Operation standard: Inject water until the outlet overflows before starting.

Impeller blockage/wear

Blockage of the flow channel by debris (especially when containing particles>0.5mm) or corrosion and deformation of the impeller.

Solution: Remove and wash the impeller, and install a filter (aperture ≤ 1mm) at the inlet.

Mechanical seal leakage

The aging of the sealing components leads to water and air leakage, and it is necessary to replace the corrosion-resistant material sealing ring.

3. Media and environmental factors

Liquid viscosity too high

When transporting high viscosity media such as crude oil, an internal mixing self-priming pump should be used instead.

Insufficient water source

The water inlet is not submerged at least 30cm below the liquid level, or the water source is depleted.

4. Equipment malfunction

Motor reversal: buzzing but not producing water, switch the power supply two-phase wires.

Voltage too low: insufficient speed, weak suction, stabilize to rated voltage ± 5%.

Bearing damage: abnormal vibration and noise. Replace the bearing and correct the axis.