Building Regulations Part L – Dwellings

Building regulations are changing and energy efficiency in homes is growing ever more important.

Part L of the Building Regulations acknowledges this, requiring housing providers to take steps to reduce carbon emissions.

We’re familiar with BS7593:2019, the British Standard for the preparation, commissioning and maintenance of domestic central heating and cooling water systems. This code of practice provides guidance to drive the adoption of best practice in entire system health, not simply appliance protection.

The code of practice states that a chemical clean, followed by a fresh-water flush and the fitting of a permanent in-line filter should be undertaken, before an inhibitor is applied for all new heating systems. The concentration of additives and the cleanliness of system water should be checked after commissioning and annually thereafter throughout the life of the system. Additionally, inhibitor should be re-dosed at 5-year intervals since last treatment, or a full laboratory analysis of system water should be undertaken, with biocide required in cooling and low temperature heating.

Building Regulations have since been updated to include system specific reference for commissioning, enforcing the best practice approach.

Within the revised Approved Document Part L for Dwellings, Section 8.6 covers commissioning of hot water systems for space and domestic hot water heating. This emphasises that ‘Before a new heating appliance is installed, all central heating and primary hot water circuits should be thoroughly cleaned and flushed out. A suitable chemical inhibitor should be added to the primary heating circuit to protect against scale and corrosion. Domestic central heating systems should be prepared and commissioned to BS7593:2019.’

The Benchmark commissioning checklist can be used to show that commissioning has been carried out satisfactorily for the heating and hot water system and its heat generation source. Benchmark is now available as a digital app making it easier and more convenient for installers to prove compliance with the regulations. For more information visit

In summary:

Commissioning is now required for new and existing systems

All heating systems should be prepared and commissioned to BS7593:2019

Benchmark is the preferred method of proving commissioning regardless of the heat generation source.