8 Reasons Your Centrifugal Pump Has Low Flow

In Seinfeld’s infamous episode “The Shower Head”, Jerry’s apartment building has new shower heads installed that leaves Jerry, Kramer, and Newman’s hair looking a little flat. The situation becomes so frustrating, they eventually resort to buying black market shower heads.

Not unlike Jerry and his friends, when low flow problems occur with centrifugal pumps, it can leave your process’s performance a little flat. The problem can also be frustrating, but don’t necessarily blame the pump (or resort to a black market pump!) just yet. Check these simple things first.

1. Reversed Impeller Rotation

This may seem like a no-brainer, but it really is a common problem. When wiring the pump’s motor to power, it’s important to test which way the motor is turning first. “Bump Starting” the motor is a common practice where the motor is started without the pump hooked up to ensure proper rotation of the shaft. If the motor turns the wrong way, the impeller could potentially back off the shaft, causing serious damage to the internals.

2. Clogged Suction

Make sure the suction pipe is free and clear of debris. Less flow into the pump, will obviously yield less flow out of the pump.

3. Worn impeller, wear ring, wear plate

If the vanes on the impeller are worn, the hydraulic capacity of the pump is reduced. Same with the wear ring and wear plate. When clearances open up due to wear, more recirculation occurs inside the pump, reducing the pump’s flow.

4. Excessive Clearances 

If clearances are too wide for the type of fluid pumped, excessive slip will occur. Fluid will continue to recirculate inside the pump, yielding lower flow out of the pump.

5. Debris in the impeller

If the eye of the impeller is plugged with debris, it removes the hydraulic capacity of the impeller to create an area of low pressure.

6. Closed Discharge or Suction Valve

Again, this one seems really simple, but something that can be easily overlooked.

7. Open Bypass Valve

Check to make sure the flow isn’t being diverted somewhere else through a bypass valve.

8. Vortexing

This is more common with pumps in suction lift conditions, like a self-priming pump, or a vertical turbine. Make sure you’re meeting minimum submergence requirements to prevent vortexing.

Centrifugal pumps producing inadequate flow can cause problems not only for the pump itself, but also for other equipment in the process. If you’ve tried all the points listed above, it may be a bigger system issue. Get an engineer, well versed in fluid processes, involved to help you get back on track faster.

Got problems with a low flow pump? Ask us about it! We gladly provide technical assistance to businesses and municipalities in Wisconsin and upper Michigan.