Expansion Vessel Meibes BASEFLEX 18/1.5 6 bar for Central Heating (25302)

Meibes BASEFLEX 18/1.5 is an expansion vessel for central heating systems with an 18 litre effective capacity and a factory pre-charge of 1.5 bar. Engineered to compensate for thermal expansion of heating water up to a maximum system pressure of 6 bar, this vessel helps maintain stable pressure, reduces stress on pumps and valves, and protects the heating circuit from overpressure cycles. It is designed for residential and small commercial installations where a compact, reliable membrane-type expansion vessel is required.

Advantages

The vessel provides reliable pressure stabilization and thermal expansion compensation without mechanical complexity. Its rated 6 bar maximum pressure and 18 l capacity suit a wide range of domestic and light-commercial heating circuits. The integrated pre-charge eases initial commissioning and reduces the need for immediate adjustment. The membrane design separates the water and gas sides to prevent corrosion and preserve performance over time.

Suitable for

• Residential central heating systems
• Small commercial heating circuits
• Systems requiring an 18 l expansion volume and 1.5 bar pre-charge
• Replacement of existing membrane expansion vessels of similar size

Key specifications

• Effective volume: 18 litres
• Factory pre-charge pressure: 1.5 bar
• Maximum allowable system pressure: 6 bar
• Membrane-style separation between water and gas chamber
• Compact cylindrical design suitable for wall- or floor-mounted installation near the boiler or accumulator

How to use

Install the expansion vessel on the system’s filling or return line according to the hydraulic layout and local regulations. Ensure the vessel pre-charge matches the static pressure of the installation when the system is cold; adjust the pre-charge if required before connecting to the system. Securely mount the vessel, connect using appropriate fittings and isolation valves, and perform a leak test. After filling and venting the heating circuit, verify operating pressure remains within the allowed range during heating cycles and re-check the pre-charge periodically.

Usage recommendations

Check pre-charge pressure before installation and during routine maintenance, ensure compatibility with system maximum pressure and fluid type, and follow local codes for mounting and pressure-relief arrangements.