CIBSE Commissioning Code W: Water Distribution Systems describes the requirements for commissioning water distribution systems in buildings. It complements BSRIA Application Guide BG2/2010, which describes how commissioning is to be carried out. 

Correct commissioning is a requirement of Part L of the Building Regulations and is vital in ensuring that water distribution systems in a building perform as they were designed to. Approved Document L2A of the Building Regulations 2010 states that ‘notice of completion should be given to the relevant Building Control Body (BCB) confirming that:

• A commissioning plan has been followed so that every system has been inspected and commissioned in an appropriate sequence and to a reasonable standard; and 
• The results of tests confirm that the performance is reasonably in accordance with the actual building design, including written commentaries where excursions are proposed to be accepted.

Furthermore, the Building Control Body may not be able to provide a completion certificate until it receives the commissioning notice. 

Commissioning is critical to achieving the safe, effective and efficient operation of hydronic systems (defined as those which use water as the medium for heat exchange) and must include circuit balancing of the distribution system. A properly commissioned system optimises performance and ensures good quality living / working environments. 

The latest version of CIBSE Code W includes recommendations for achieving accurate commissioning of variable volume hydronic systems with ultra-low flows. The problem of measurement of low flows has become increasingly common, as space heating loads have reduced in response to higher internal heat gains and improved building insulation. Recommended techniques include the subtraction method, which is well suited to SAV’s FloCon Ultra Low Flow commissioning modules.