Self-Priming Pumps

What Does Self-Priming Mean?

A self-priming pump can evacuate air from the suction line and create the vacuum needed to draw fluid up to the pump on its own — without external assistance and without needing the suction side pre-filled with liquid. The capability matters because real-world fluid transfer rarely happens with the pump conveniently flooded at all times. Suction lines empty between cycles. Drum levels drop. Sumps and tanks fill and empty. A pump that can't self-prime requires manual intervention, foot valves that fail, or priming systems that add cost and failure points.

Self-priming pumps come in two broad categories: pumps with self-priming features added (centrifugal pumps with priming chambers, jet assemblies, or vacuum-assist systems) and pumps that are inherently self-priming by design (positive displacement pumps like diaphragm and peristaltic). The inherent self-primers tend to be more reliable because the capability is built into how the pump physically works rather than added as a supporting system that can fail.

Why AODD Pumps Are Inherently Self-Priming

AODD pumps work by alternately flexing two flexible diaphragms inside opposing pump chambers. As compressed air pushes one diaphragm out, fluid discharges through a check valve. As the same air movement pulls the other diaphragm in, that chamber expands — creating suction that draws fluid in through the inlet check valve. This suction-creating motion happens on every cycle whether the pump is full of fluid, partially full, or completely dry.

The result: an AODD pump can start dry, evacuate air from a suction line up to roughly 20 feet of vertical lift (depending on configuration), and begin moving fluid without manual priming. Once primed, the pump continues operating normally. If the suction line empties again between cycles, the pump re-primes itself automatically.

This is fundamentally different from how centrifugal pumps create flow. A centrifugal pump uses an impeller to add velocity to the fluid; if there's no fluid in the impeller chamber, there's nothing to accelerate, and the pump won't prime without a flooded suction or a separate priming system. That's why centrifugal pumps marketed as "self-priming" typically have additional chambers, jet assemblies, or vacuum-assist systems bolted on — they're solving a problem that AODD pumps don't have in the first place.

Self-Priming AODD vs. Self-Priming Centrifugal Pumps

If you've been comparing self-priming centrifugal pumps for an industrial application, AODD diaphragm pumps are worth evaluating side-by-side. Centrifugal self-primers solve the priming problem with auxiliary systems: priming chambers, recirculation features, or vacuum-assist setups. These work — but they add cost, mechanical complexity, and failure points.

AODD self-priming is structural. There's nothing extra to fail because there's nothing extra in the first place. Beyond self-priming itself, AODD pumps add capabilities that centrifugals can't match: handling solids and slurries without erosion, running dry without damage, intrinsic safety in hazardous environments (no electricity), and seal-less operation. The trade-off is flow rate — centrifugals can move more volume at higher discharge pressures.

For most industrial transfer, dewatering, drum unloading, and chemical diaphragm pump work, AODD pumps are the better fit. For very high-volume, low-viscosity transfer in clean fluids, centrifugals retain the edge.

For a deeper comparison specific to AODD and centrifugal pumps, see the blog post on why "either works" may actually be wrong.

Browse Self-Priming AODD Pumps

The PSG® Store carries the full Wilden® and All-Flo™ AODD lineup — every pump in the catalog is self-priming by design. There's no separate "self-priming line" because the entire AODD lineup is self-priming. Both brands ship from the PSG® Store with manufacturer's warranty and access to genuine diaphragm pump parts.

Find the Right Self-Priming Pump for Your Application

Use the filters above to narrow the catalog, or use the pump finder if you need help matching a self-priming AODD pump to your specific application requirements. In-stock pumps ship same-day; non-stocked configurations ship direct from the manufacturer.

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