Oberdorfer 405M-04-M26 Bronze Flexible Impeller Pump — 3/4 HP, 1725 RPM, 115/230V ODP, 25 GPM Self-Priming Utility Pump
The Oberdorfer 405M-04-M26 is a close-coupled bronze flexible impeller pump driven by a 3/4 horsepower, 1725 RPM, single-phase ODP motor rated for 115/230 volts. Built with an all-bronze pump body and a stainless steel shaft, it's engineered to deliver dependable, corrosion-resistant performance in demanding wet environments. The neoprene rubber impeller runs inside a precision cam-style pumping chamber, and because there is only one moving part, maintenance is minimal and impeller replacement is straightforward without removing the pump from the line. A mechanical seal keeps the unit tight and serviceable over the long term.
What makes this pump genuinely useful across a range of jobs is its self-priming capability — when fully primed, it can pull a suction lift of up to 15 feet and move up to 25 GPM, making it equally at home in portable fluid transfer setups, industrial washdown stations, aquaculture recirculation systems, irrigation supply lines, and general water handling wherever a compact, reliable pump is needed. The motor mounts to a NEMA 56C face with an aluminum adapter plate, and the pump can operate in either rotational direction for added installation flexibility. Liquid temperature range runs from 40°F to 180°F with the standard neoprene impeller.
Key Features
- All-bronze pump body for maximum corrosion resistance
- Neoprene rubber flexible impeller with cam-actuated pumping action — no metal-to-metal contact
- Stainless steel pump shaft for durability and corrosion protection
- Mechanical seal design (Model 405M) for reliable long-term sealing
- Self-priming capability with suction lift up to 15 feet when primed
- Only one moving part — easy impeller replacement without full disassembly
- Bidirectional rotation capability
- Optional vacuum switch shut-off available
- Nitrile (Buna-N) impeller available as an alternative for oil-contaminated water or kerosene service
Applications
- Potable and non-potable fresh water transfer
- Salt water and water-solution handling
- Industrial fluid transfer and washdown
- Aquaculture and aquarium recirculation
- Irrigation and agricultural water supply
- Portable fluid handling in construction and industrial settings
- Bilge, baitwell, and washdown service
- General utility liquid transfer where self-priming is required
Specifications
- Part Number: 405M-04-M26
- Pump Type: Close-coupled bronze flexible impeller pump
- Motor Power: 3/4 HP
- Motor Speed: 1725 RPM
- Voltage: 115/230V single-phase
- Motor Type: ODP (Open Drip Proof)
- Motor Frame: NEMA 56C with aluminum adapter plate
- Max Flow Rate: 25 GPM at 0 PSI
- Max Pressure: 43 PSI (at 7 GPM / 100 ft head)
- Suction Lift: Up to 15 feet (fully primed)
- Inlet Port: 1" NPT and 1-1/2" hose
- Discharge Port: 1" NPT and 1-1/2" hose
- Impeller Material: Neoprene rubber (Nitrile/Buna-N available)
- Shaft Material: Stainless steel
- Pump Body Material: Bronze
- Seal Type: Mechanical seal
- Liquid Temperature Range: 40°F to 180°F (standard neoprene impeller)
- Bearing Type: Ball/ball
- Duty Rating: Continuous duty
- Phase: Single-phase
Frequently Asked Questions
Q: Does the Oberdorfer 405M-04-M26 need to be primed before first use?
Yes. On initial startup, the pump must be primed with liquid before operation. Running it dry — even briefly — will rapidly degrade the neoprene impeller due to the high friction generated without lubrication. Once primed, the pump is self-priming and will maintain suction lift going forward.
Q: Can this pump handle liquids other than fresh water?
The standard neoprene impeller is compatible with fresh water, salt water, and mild water-based solutions within a temperature range of 40°F to 180°F. It is not suitable for gasoline, petroleum-based solvents, or viscous oils. If oil-contaminated water or kerosene service is required, a Nitrile (Buna-N) impeller is available as an option, though with a reduced service life.
Q: What should be done if the pump will not be used for an extended period or is exposed to freezing temperatures?
Drain the pump by loosening the cover screws and fill the pump chamber with a methyl alcohol-based antifreeze such as Zerex or Dowgard. Do not allow liquid to freeze inside the pump body, as this can cause cracking and permanent damage.
Q: Can the pump rotation direction be reversed?
Yes. The 405M-04-M26 flexible impeller pump is designed to operate in either rotational direction, which provides added flexibility during installation and piping layout.
Q: Is this pump suitable for continuous-duty operation?
Yes. The ODP motor paired with this pump is rated for continuous-duty service and includes built-in overload protection, making it appropriate for applications that require sustained run times.
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