Unvented Water Heaters

General Traditionally only vented hot water storage systems have been used within the UK, and until 1985 the installation of an unvented hot water storage system with a capacity greater than 15 litres directly connected to the cold water mains supply was illegal. After G3 of the Building Regulations 1985 was introduced, together with a relaxation of the appropriate Water Byelaws, systems of this type were then allowed to be installed within the UK. There are important differences between unvented hot water storage systems and vented hot water storage systems and it is essential that unvented hot water storage systems are designed and installed with the correct safety devices as stated within G3 Building Regulations.

It is also essential that unvented systems are installed by competent installers i.e. one holding a current Registered Operative card for the installation of unvented domestic hot water storage systems.

Requirements
The requirements of the Building Regulations G3, state that all systems must be either:

• A. approved by a member body or the European Organisation for Technical Approvals (EOTA) - operating a technical approvals scheme e.g. meeting the relevant requirements of G3  ;or
• B.approved by a certification body having National Accreditation of Certification Bodies (NACB) accreditation and testing to the requirements of an appropriate standard that will ensure that the requirements of Regulation G3 will be met e.g. BS 7206:1990, or
• C. the subject of a proven independent assessment that will clearly demonstrate an equivalent level of verification and performance to a. or b. above.
  Kiwa is one of several organisations within the UK who are deemed to be suitable to approve unvented hot water storage systems to the requirements of the Building Regulations.