Source: gasapplianceguide.co.uk
To ensure that unvented cylinders are fitted correctly, safely and by competent installers the Government introduced Building Regulations (G3). These Regs cover any vessel that contains more than 15 litres of hot water under pressure.
NEVER attempt to install an unvented cylinder unless you are trained to do so. The consequences could be catastrophic.
http://www.youtube.com/watch?v=Cv178a60Ypg&feature=related
Carefree, January 2011
