4.4 Gal. Hydronic Heating Expansion Tank

Zilmet ZHT18-30 Hydronic Expansion Tank – 4.4 Gallon, 1/2" NPT, 60 PSI Max

The Zilmet ZHT18-30 is a diaphragm-type hydronic expansion tank engineered for closed-loop hot water heating systems. With a 4.4-gallon total capacity, this model is designed to absorb excess pressure caused by thermal expansion, maintaining system stability and extending component life.

This unit features a carbon steel shell with a baked epoxy-polyester coating and a certified synthetic rubber diaphragm. Its side-mounted 1/2" NPT connection and compact dimensions allow for integration into wall-mounted or floor-mounted hydronic systems with space constraints.

Key Product Features

• Total Volume: 4.4 gallons (16.5 liters)
• Construction: Welded carbon steel with corrosion-resistant external coating
• Diaphragm: Butyl rubber, replaceable, designed for optimal pressure separation
• Connection: 1/2" NPT female thread (side-mounted)
• Factory Pre-Charge: 12 psi (adjustable to match system requirements)

Performance Specifications

• Maximum Working Pressure: 60 psi
• Maximum Temperature: 230°F (110°C)
• Diameter: 11.4 inches
• Height: 14.8 inches
• Certifications: CE and NSF/ANSI 61 compliant
• Warranty: 5-year limited (manufacturer)

Installation Notes

The ZHT18-30 is intended for installation in closed-loop hydronic heating systems. Mounting should allow access to the air valve for pressure adjustment. System pressure must be checked and matched prior to final connection. Installation must conform to applicable plumbing and mechanical codes and should be completed by qualified personnel.

Recommended Applications

Suitable for residential and light commercial hot water boiler systems requiring pressure stabilization. Compatible with wall-hung boilers, baseboard systems, and radiant floor heating loops where expansion volume control is needed to prevent overpressurization.