ZWL Self-Priming Pump Troubleshooting & Maintenance

A ZWL direct-coupled self-priming sewage pump is a simple, reliable machine, so when something goes wrong the cause is usually straightforward. Here’s a symptom-by-symptom guide to the common ones and how to fix them.

Won’t pump after starting

Usually an air or priming problem:

• Air leak on the suction line → find and seal it (the most common cause).
• No or too little liquid in the pump body → top up the stored priming liquid.
• Blocked suction line or a leaking gauge/fitting → clear the line and check fittings.

Low flow

• Partial blockage in the suction line → clear it.
• Blocked impeller passage → clear the impeller.
• Low voltage / speed too low → check the electrical supply.
• Suction line too long or too many right-angle bends → shorten it and reduce elbows.

Excessive noise or vibration

• Pump and motor shafts not concentric → re-align to within ~0.1 mm.
• Bent pump shaft → replace the shaft.
• Badly worn bearings → replace them.

Bearing running too hot (over 70°C)

• Too much or too little oil → adjust to the correct level.
• Degraded oil → change it.
• Damaged bearing → replace it.

Leaking at the pump body

• Worn mechanical seal → replace the seal.
• Worn sealing ring → replace the ring.

A little routine care goes a long way

Keep the suction side sealed, watch the bearing temperature, keep the medium within limits (≤80°C, solids under ~15% of weight), and don’t let the pump body run dry. Catching a worn seal or bearing early is cheap; ignoring the warning signs is not.

Operating limits

• Bearing temperature: ≤70°C
• Medium temperature: ≤80°C
• Solids load: ≤15% of medium weight
• Flow rate: 8–800 m³/h
• Material: cast iron or stainless steel

Need spare parts — seals, sealing rings, impellers, bearings? Tell us the model and we’ll get you the right ones.