Flojet G257 Series Air-Operated Double Diaphragm Pump

Flojet G257 Series Air-Operated Double Diaphragm Pump – Up to 10 GPM

The Flojet G257 Series Air-Operated Diaphragm Pump is a heavy-duty dual air-operated double diaphragm (AODD) pump system designed for general commercial and industrial fluid-transfer applications. Flojet specifies the G257 Series for applications requiring reliable transfer of a broad range of compatible liquids and chemicals.

The G257 Series provides flow rates of up to 10 GPM (approximately 38 LPM) and operates using a 20–100 PSI (1.4–6.9 bar) air supply. Because the pump is pneumatically driven, it does not require an electric drive motor at the pump, making it useful in many industrial fluid-handling installations.

Depending on the exact G257 model, different diaphragm and valve materials are available to suit different fluid-compatibility requirements.

Main Features:

• 💨 Air-Operated Design – Pneumatically powered for commercial and industrial fluid-transfer applications.
• 🔄 Double Diaphragm Technology – Positive-displacement, air-operated double diaphragm design.
• 💧 High Flow Capacity – Delivers up to 10 GPM / approx. 38 LPM.
• 📈 20–100 PSI Air Supply – Designed for an air supply range of approximately 1.4–6.9 bar.
• ⬆️ Self-Priming – Up to 15 ft (4.5 m) dry and 20 ft (6.1 m) wet priming capability.
• 🛡️ Chemical-Resistant Construction – Glass-reinforced polypropylene housing with different elastomer options according to model.
• ⚙️ Hastelloy Springs – Used within the check-valve assemblies.
• 🔧 Compact Dual-Pump Assembly – Provides higher flow while maintaining a relatively compact installation footprint.
• 🌡️ Wide Operating Temperature Range – Suitable for liquids from approximately 40°F to 120°F (4.4°C to 48.9°C).
• 🔌 No Electric Pump Motor Required – Operation is powered by compressed air.

Main Specifications

G257 Series Model Options

Flojet's current G257 model table lists four primary configurations:

HB = Hose Barb. Exact air-inlet configuration should be confirmed against the individual model before ordering.

G257301A / G257302A – FKM Versions

These models use FKM diaphragms and FKM-based check-valve components. Flojet's documentation associates FKM configurations with compatible applications involving various acids, oils, solvents and certain hydrocarbons, subject to chemical compatibility verification. 

G257501A / G257502A – EP/PP Blend Versions

These variants use EP/PP blend diaphragms, providing another elastomer option for applications involving compatible liquids.

Main Applications:

The Flojet G257 Series can be considered for compatible commercial and industrial applications such as:

• 🧪 Chemical transfer and dispensing
• 🧴 Detergent and cleaning-fluid transfer
• 💧 Water and compatible liquid transfer
• 🏭 Industrial fluid-handling systems
• ⚙️ Process-fluid transfer
• 🧼 Commercial cleaning systems
• 🚗 Automotive-service fluid systems
• 🛢️ Compatible oil and lubricant transfer
• 🔄 Fluid circulation and dispensing systems

Important: Fluid compatibility depends strongly on the selected diaphragm, check-valve and seal materials. Verify chemical compatibility before use.

How It Works

Compressed air operates the diaphragms in an alternating motion. As one diaphragm creates suction and draws liquid into the pump, the opposite diaphragm pushes liquid toward the discharge side.

Check valves control the direction of liquid flow, creating continuous positive-displacement pumping without requiring a conventional electric pump motor.

This operating principle provides good self-priming capability and makes the G257 suitable for demanding fluid-transfer applications.

• Dimensions

Flojet's dimensional drawing gives the G257 dual-pump assembly an overall envelope of approximately:

• 12.88" (328 mm) × 10.06" (256 mm) × 5.19" (127 mm max.)

Flojet advises consulting the manufacturer where precise dimensional details are required.

Main Benefits:

• High flow of up to 10 GPM
• Pneumatic operation
• Positive-displacement pumping
• Excellent self-priming capability
• Multiple elastomer configurations
• Corrosion-resistant polypropylene construction
• Suitable for a broad range of compatible fluids
• Compact dual-pump arrangement
• Commercial and industrial-duty design
• Straightforward installation and servicing