4 Gal. Hydronic Expansion Tank for Boiler System with Valve

Amtrol FILL-TROL – 4.4 Gallon Expansion Tank with Integral Fill Valve for Closed-Loop Hydronic Systems

The Amtrol FILL-TROL is a pre-pressurized expansion tank designed for residential hydronic heating systems. This model combines a diaphragm-type thermal expansion tank with a factory-installed automatic fill valve. The integrated design simplifies installation and ensures proper system pressurization without requiring a separate fill valve assembly.

Engineered for closed-loop boiler systems, the FILL-TROL manages thermal expansion during heating cycles, maintaining stable system pressure and protecting components from over-pressurization. Its deep-drawn steel construction, sealed air cushion, and high-temperature butyl/EPDM diaphragm provide consistent performance under demanding conditions.

Key Technical Details

• Total Volume: 4.4 gallons
• Acceptance Volume: 2.5 gallons
• Pre-Charge Pressure: 12 psig (factory set)
• Maximum Working Pressure: 100 psi
• Maximum Temperature: 240°F
• Connection Size: 1/2" NPT
• Dimensions: 11" diameter x 16" height
• Diaphragm Material: Butyl/EPDM composite
• Warranty: 5-year limited

System Integration Benefits

• Combined Fill Valve and Expansion Tank: Factory-assembled unit streamlines installation and ensures compatibility
• Pre-Pressurized Design: Maintains proper pressure across temperature ranges to reduce air ingress and component stress
• Sealed Air Chamber: Reduces maintenance and eliminates the need for periodic air recharging
• Steel Shell: Deep-drawn and finished with corrosion-resistant coating for long-term reliability

Installation Considerations

Mount the FILL-TROL vertically on the system’s cold water return line near the boiler. Ensure the connection point supports both mechanical stress and code requirements for closed-loop expansion systems. The integrated fill valve includes a threaded inlet for system supply and a regulating assembly preset at the factory. Adjustment of pre-charge pressure may be required to match system static fill conditions. Installation should be performed by qualified HVAC or plumbing professionals to ensure compliance with local code and equipment specifications.

Recommended Applications

The FILL-TROL is intended for sealed, hot water heating systems where an expansion tank and pressure-regulating valve are both required. This includes residential hydronic baseboard, panel radiator, and radiant heating systems with moderate water volume and operating pressure below 100 psi.