Wastewater Pumps · Positive-Displacement Pumps
What Is a Positive-Displacement Pump?
A positive-displacement pump moves a set amount of material during each cycle or turn.
Instead of adding velocity with an impeller, this pump traps liquid and pushes it forward. Common wastewater examples include progressing-cavity, rotary-lobe, diaphragm, piston, and peristaltic pumps. They are often used for sludge, polymer, and chemical feed.
Flow is closely related to pump speed when the pump and material are in good condition. Pressure depends mainly on resistance in the discharge system. That difference from a centrifugal pump is important.
A blocked discharge can make pressure rise quickly. Positive-displacement systems need a safe pressure-relief path or other protection. Never run one against a closed valve unless the design and procedure clearly allow it. Verify the discharge path before startup.
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