General Specification

Compression fittings are designed to mechanically form joint between the fitting and the pipe. When tightening the nut, you are compressing the olive onto the tube, creating a permanent seal.

Flowflex Compression Fittings are manufactured in the UK to the BS EN 1254-2 standard. Made from brass bar which conforms to British (CZ) and European (CW) material designs, they are available in four finishes:


Flowflex operates a quality management system audited by the British Standards Institute for the manufacture and supply of fittings and components for use in all applications of the HVAC industry.

Flowflex reserve the right to alter the product ranges and specifications associated with its products without prior notice

Working Conditions

Maximum Temperatures (°C) Maximum Pressures (bar)
6mm < 54mm 54mm < 108mm
30 16 10
65 10 6
110 6 4
120 5 3

Electrical Continuity

Equipotential Bonding forms an important part of an installation, which ensures that all metalwork may be earthed or at least has the same potential to reduce the risk of equipment damage and personal injury. Isolated fittings or valves are not required to be bonded.

Flowflex Compression Fittings provide guaranteed electrical continuity when correctly assembled with carbon steel, copper or stainless steel tube.

Our Compression Fittings however will not provide electrical continuity when connected to non-metallic tube such as PEX or MDPE.

After all plumbing work has been completed, always ensure continuity checks are conducted by a qualified electrician in accordance with regulations (BS 7671).

Stress Corrosion Cracking

Stress Corrosion Cracking (SCC) occasionally occurs in brass components. It normally always caused during installation through over-tightening or contamination with a Stress Cracking Agent.

Ammonia or Ammoniacal Compounds are the most typical cause of SCC, which can be found in cleaning fluids, refrigeration gases, sewage waste products, building materials, insulating materials (especially foams) and flame and smoke retarding treatments.

Moisture is a catalyst in the SCC process. Moisture allows the corrosive substance to collect and become more concentrated, which can be a particular problem in chilled water installations, where insulating materials allow the condensed moisture to be retained and kept in close contact with the surface.

For this reason it is not recommended to use brass components in chilled water applications. Instead, you might use copper based fittings which are not susceptible to SCC.

If brass components are chosen, then they should be assembled exactly in accordance with our instructions and securely bound by a moisture barrier to prevent moisture build up on the surface.

Overall SCC can be avoided with adherence to good installation practice and adherence to our instruction.

The following installation practices should be adhered to when installing brass components in order to avoid Stress Corrosion Cracking:

  • Do not overtighten brass nuts.
  • Use a drop or two of light oil on the threads of fittings of sizes 35mm and above.
  • Use correctly fitting spanners.
  • Avoid contaminating the threads or nuts with jointing compounds.
  • Use parallel threaded adaptors to avoid stressing the female threaded ends.

Minimise the risk of contamination from a potential corrosive substance. Wrapping susceptible fittings in a vapour barrier or applying impermeable paints can be helpful in preventing contact with a corrosive substance.