SEAFLO 41 Series 12V 3.3GPM 35PSI Water Pressure Pump

Automatic freshwater pressure for boats and mobile systems

The SEAFLO SFDP1-033-035-41 is a 12V DC four-chamber diaphragm demand pump delivering up to 3.3 GPM (12.5 L/min) at open flow with a 35 PSI shut-off setting. The built-in pressure switch starts when a tap opens and stops when the system repressurises.

It suits freshwater systems on boats, yachts, campervans, caravans and remote cabins, typically supplying up to three fixtures. The internal bypass reduces rapid cycling during small water demand.

Performance and design features

• Four-chamber diaphragm provides smooth flow and reduced pulsation.
• Automatic on-demand pressure switch.
• Internal bypass helps manage small flows without constant switch cycling.
• Self-primes up to approximately 1.8 m suction lift.
• Run-dry capable for accidental loss of supply, but not intended for deliberate prolonged dry operation.
• Quick-attach ports support fast installation and winterisation.
• Rubber mounting feet help isolate vibration and noise.
• Suitable for fresh or salt water within material limits; flush thoroughly after salt-water use.

Technical specification

Compatibility and installation checks

• Confirm a 12V DC supply and size the fuse and cable for the 8.5 A maximum draw and cable length.
• Suitable for approximately one to three fixtures, depending on simultaneous demand and plumbing losses.
• Confirm the existing plumbing accepts SEAFLO quick-connect ports; adapters may be required when replacing another brand.
• Install an inlet strainer and flexible hoses, keep the suction side airtight and mount in a dry ventilated location.
• All taps, heaters, filters, accumulators and fittings must tolerate at least 35 PSI and the operating temperature.
• Not submersible and not suitable for fuel, oil, sewage, bilge water or abrasive liquid.
• Package: one 41 Series pump. Confirm pictured fittings; strainer, hose, fuse and main wiring may be separate.

Frequently asked questions

Does it start automatically when a tap opens?

Yes. The integrated pressure switch provides on-demand operation.

Does it need an accumulator tank?

Not normally in a correctly configured system, although a compatible accumulator can further smooth flow and reduce cycling.

Can it replace any 12V pump?

No. Compare current, pressure, flow, ports, dimensions and mounting pattern before ordering.

Can it be used as a bilge pump?

No. It is a pressure-water diaphragm pump and must not be submerged.