13.2 Gallon, Hydronic Expansion Tank, Inline

Zilmet ZHT50-90 – 13.2 Gallon Expansion Tank for Closed-Loop Hydronic Systems

The Zilmet ZHT50-90 is a 13.2-gallon diaphragm expansion tank designed to control pressure changes in closed-loop hydronic heating systems. It compensates for thermal expansion as system fluid is heated, minimizing fluctuations that can compromise the performance of boilers, circulators, valves, and other system components.

This tank features a fully welded carbon steel shell, an internal synthetic SBR rubber diaphragm, and a corrosion-resistant external coating. The pre-charged air chamber is field-adjustable to match system static pressure, and the diaphragm design maintains a physical barrier between the air and water to reduce saturation and waterlogging over time.

System Integration Features

• Nominal Volume: 13.2 gallons
• Connection: 3/4" NPT side outlet
• Maximum Working Pressure: 90 psi
• Shell Construction: MIG-welded carbon steel
• Diaphragm Material: Certified synthetic SBR rubber

Application and Performance

• Designed for Closed-Loop Systems: Intended for hydronic heating circuits utilizing water or glycol-based heat transfer fluids.
• Pre-Charged and Adjustable: Supplied with factory air charge; adjust to match system static pressure during installation.
• Side Connection Port: Allows horizontal or vertical mounting depending on system design constraints.
• Corrosion Protection: Epoxy-polyester powder-coated exterior provides durability in mechanical rooms or utility areas.

Installation Guidelines

The ZHT50-90 should be installed on the return side of the hydronic loop, near the boiler or air separator. Position the tank vertically with the connection facing down or sideways, depending on mounting hardware and system configuration. Pre-charge pressure must be verified and adjusted prior to filling the system. Installation should follow local mechanical codes and best practices for expansion tank sizing and placement. Qualified plumbing or HVAC personnel are recommended for setup and commissioning.

Operational Use Case

Best suited for mid-size residential or light commercial systems with medium fluid volumes. The ZHT50-90 provides consistent thermal expansion buffering in systems requiring higher operating pressures, including multi-zone heating layouts or extended piping networks.