I think the pressure relief device has blown. It’s a safety device on the bottom of the heating tank.
It is fairly easy to replace however there is usually something that causes it to blow, often a kink in the hose or the showerhead is blocked, so check this before fitting the new PRD.
http://www.shower-warehouse.co.uk/erol.html#24342x24578
You can then purchase the items online or call the office on 0131 443 9917 pressing option # 1 for spares.
http://www.shower-warehouse.co.uk/erol.html#588X0
Complete spare part number and diag here
http://www.shower-warehouse.co.uk/erol.html
slightly cheaper here
http://www.shower-spares.co.uk/triton/triton_opal.htm
Helper
June 2009