HP-18 is an 18-liter (4.5-gallon) expansion tank specifically engineered for closed-loop hydronic heating and cooling systems. It effectively absorbs expanded fluid volume to control pressure build-up, ensuring the safety and stability of residential or commercial setups.
Built for high-performance environments, the tank supports a maximum operating pressure of 10 bar (150 psi) and temperatures up to 130°C (266°F). It is factory pre-charged to 1 bar (15 psi) and is fully compatible with propylene glycol mixtures of up to 50%.
With a diameter of 28.0 cm and a height of 37.75 cm, this mid-sized tank offers a compact yet highly reliable solution. It is designed for convenient installation alongside non-potable water systems, delivering dependable expansion absorption in a space-saving footprint.
Product Overview
The HP-18 is an 18-liter (4.5 gallon) hydronic expansion tank engineered specifically for closed-loop hydronic heating and cooling systems. As the fluid in your climate-control system changes temperature, it expands and contracts; the HP-18 safely absorbs this expanded fluid volume, effectively controlling the excessive pressure generated inside the system and preventing potential hazards.
Built with a robust sheet steel tank, the HP-18 utilizes a specialized, high-temperature-resistant EPDM rubber diaphragm to ensure exceptionally safe and reliable operation. To guarantee supreme durability, every single Hydro-Plus model is subjected to rigorous hydraulic testing at a pressure 1.5 times higher than the design pressure.
Manufactured with premium materials, welded according to strict ASME & EN procedures by certified welders, and compliant with IAPMO and EN standards, Aquasky HYDRO-PLUS tanks are the ultimate safety choice for your hydronic heating system, delivering a long service life and dependable performance.
Certification
Specifications and Technical Data
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| Parameter | Value |
| Model Number | HP-18 |
| Total Tank Volume | 18 liters / 4.5 gallons |
| Diameter | 28.0 cm / 11.0 inches |
| Height | 37.75 cm / 14.9 inches |
| Net Weight (NW) | 3.4 kg / 7.5 lbs |
| Gross Weight (GW) | 3.8 kg / 8.4 lbs |
| Shipping Volume | 1.08 CUF |
| Max. Operating Temperature | 130°C / 266°F |
| Factory Pre-charge | 1 bar | 15 psi |
| Max. Operating Pressure | 10 bar | 150 psi |
| Connection | 1/2" Cacbon Steel / Stainless Steel |
| Diaphragm Material | High-temperature resistance EPDM Rubber |
| Tank Body Shell | Cold Rolled Carbon Steel |
| External Coating | Gray Paint |
| Air Nozzle Protection | Brass cap with internal O-ring |
| Pre-charge Gas | 100% Nitrogen |
Key Features & Design Advantages
How the HYDRO-PLUS Pressure Tank Works
In closed hydronic heating and cooling systems, fluid volume changes drastically as the temperature rises and falls. The HP-18 safely absorbs this expanded fluid using a sealed, compressible air cushion space. It stores the fluid securely against the high-temperature EPDM rubber diaphragm, while the air chamber compresses to accommodate the volume change. This mechanism seamlessly controls excessive pressure, protects valves and piping, and maintains safe system parameters without venting fluid.
Key benefits
Typical Applications
Frequently Asked Question (FAQ)
A: The HP-18 is engineered with a specially formulated, high-temperature resistance EPDM rubber diaphragm that safely handles extreme heating conditions up to 130°C (266°F). To guarantee it is the best safety choice for your closed-loop system, every single HP-18 tank undergoes a rigorous hydraulic test at 1.5 times its 150 PSI (10 Bar) design pressure before leaving our factory.
A: Yes, the HP-18 (4.5-gallon) is the "sweet spot" for many residential systems. It is ideally sized for mid-sized closed-loop systems, providing enough volume to absorb thermal expansion in homes with multiple radiators or modest underfloor heating circuits without taking up excessive utility space.
Downloads & Certification Links