Five Signs You Should Service or Replace Your Diaphragm Vacuum Pump

In a lab setting, vacuum pumps are expected to simply “do their job.” Often installed out of the way, they reside on shelves, in cabinets or behind the fume hood, where they transfer materials reliably, without a second thought. That is, however, until a pump eventually shows its age or malfunctions and it both literally and figuratively brings the application to a halt.

Recently, the team at Lab Manager asked us to identify the Top 5 Signs that You Should Service or Replace Your Diaphragm Vacuum Pump. This quick list is a great start, but we’d like to broaden the discussion a bit with the additional detail included below.

It’s vital for lab personnel to learn the signs of pump wear and tear. Addressing these symptoms as they take place can prevent significant downtime, costly repairs and even replacement. To keep your diaphragm pump system running optimally, monitor for the following five symptoms on a continual basis:

1. Increased bearing, motor or pneumatic noise levels.

a. Over time, as a pump wears, parts may begin to age and breakdown leading to increased operating noise levels. This is usually an indicator of the pump’s need for cleaning or standard maintenance. Consider changing the diaphragm and valves to return the pump’s noise level and performance to like new levels.

2. Slower processing or drying times due to wearing of diaphragm/valves, fouling of internal surfaces or leakage.

a. Diaphragms and valves should last a long time, but as they wear, the pump’s flowrate and end vacuum performance can suffer. Fouling of the internal surfaces may also hamper the performance of the vales and overall efficiency of the pump. This means that the pump requires more time to complete standard applications than when it was new. Changing diaphragms and valves and cleaning fouled surfaces can return the pump to like new performance. If the pump internal surfaces needed cleaning, investigate and eliminate, if possible, sources of particulates, fibers, etc., that are entering the inlet side of the pump.

3. Overheating (shutting down and restarting once the pump cools) from poor ventilation, incompatible power source or malfunctioning motor assembly.

a. KNF lab pumps are equipped with an over temperature cut off switch to prevent damage and help ensure safety. Overheating is a sign that a pump is not cooling properly, not functioning correctly or is laboring to achieve the desired performance in a given application. First check to make sure that the vents in the pump housing are not blocked or too close to a wall, etc. If the pump is properly ventilated and the power supply is appropriate to the unit, overheating can be a sign of possible issues within the motor. This pump should be returned to the manufacturer for a more detailed repair evaluation.

4. Blown fuses causing pump to shut down and not restart, due to over power or electrical short.

a. A blown fuse can indicate that a pump has been exposed to an incompatible power supply or uncontrolled power surge. If the power supply is appropriate to the pump and no power surge is detected, blown fuses may be a sign of an electrical short or malfunction within the motor. Repeatedly blowing fuses is an indicator that the pump should be returned to the manufacturer for further evaluation.

5. Slow start or stalling via startup against a vacuum or pressure beyond a pump’s capabilities, restriction of flow or blockage at the pump inlet/outlet port, or weak or damaged motor/capacitor.

a. Depending on the pump model, starting a pump against an inlet vacuum or outlet pressure may be an inappropriate use. Under these conditions, the pump may stall or start slowly causing it to overheat, underperform and/or blow fuses. Care should be taken to vent the inlet and outlet lines prior to starting and ensure that the valves and ports are free of blockages and contaminants. If the unit is normally capable of performing in this application, this may be a sign of a weakened motor or starting capacitor.


For more information about KNF Neuberger’s diaphragm vacuum pumps, visit

3 thoughts on “Five Signs You Should Service or Replace Your Diaphragm Vacuum Pump

  1. I just wanted to thank you for explaining some situations where a diaphragm vacuum pump would need to be serviced or fixed. I actually didn’t know that these could potentially overheat if there is poor ventilation. You said to check if the power supply is appropriate to the unit and I’m kind of interested to learn a bit more about how you can determine this, like if there’s a label or something similar.

    • Thank you Taylor, happy to hear that you found this post educational. Our Application Engineers can provide more details toward determining whether or not the power supply is appropriate for the diaphragm vacuum pump. The following link will take you to a brief “General Questions” form whereby you can request clarification for your unique criteria/situation –

      Alternatively, please feel free to contact our support staff through email:, or phone: (609) 890-8600

      Best of luck!

Leave a Reply to Taylor Bishop Cancel reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s