Diaphragm expansion vessel REFIX DD-18, 18L, 10 bar / 70 pcs., G3/4" threaded connection, white, for domestic hot water (DHW), wall-mounted, with non-replaceable membrane, with Rp 3/4" tee 7307900

Diaphragm expansion vessel for domestic water installations

The REFIX DD-18 diaphragm expansion vessel is a pressure maintenance device designed specifically for domestic water installations. With a nominal capacity of 18 liters and a maximum usable capacity of 13.5 liters, the product ensures optimal pressure stabilization in domestic hot water heating and distribution systems.

High-quality construction and materials

The vessel is equipped with a non-replaceable bladder membrane made of butyl, which meets the rigorous requirements of PN-EN 13831 and DIN 4807 part 5 standards. The membrane holds KTW-C and W270 certificates, guaranteeing full safety for contact with drinking water. The stainless steel connection eliminates the risk of corrosion and ensures long-term installation hygiene.

The design includes a High-Flow flow guide, which enables efficient circulation of the medium throughout the entire volume of the vessel. The tank is externally and internally coated with a special KTW-A coating, which provides additional corrosion protection and ensures compliance with the highest sanitary standards.

Operating parameters and system compatibility

The device operates at a maximum working pressure of 10 bar and a system temperature of up to 70°C. The factory-set gas pre-charge pressure of 4 bar ensures optimal working conditions immediately after installation. The standard G 3/4" connection allows for easy connection to existing installations.

The compact design with a diameter of 280 mm and a height of 418 mm (tilt diagonal approximately 503 mm) weighs only 3.04 kg, facilitating installation even in limited spaces. The product is intended exclusively for cold water installations in accordance with DIN 1988 standards.

Regulatory compliance and certification

The vessel has full approval in accordance with the Pressure Equipment Directive 2014/68/EU and the DVGW certificate (reg. no. NW-0411AT2534). The product meets the requirements of the DIN EN 13831 standard for diaphragm vessels for drinking water installations. It holds the National Institute of Hygiene (PZH) certificate, confirming safety for contact with water intended for human consumption.

The set includes an Rp 3/4" tee, and Flowjet flow fittings can be purchased optionally for even greater system functionality. Installation is possible directly on the pipeline exclusively for the medium being cold water.