Originally Posted by Fewkesy

AS above mate.
will be your plate heat exchanged pinholed internally. could only be a vessel fault if you have been running your heating but i doubt it at the moment.
this is becoming quite common at the moment due to sludge build up in the system. a good product to add while your changing it is a magnaclean. They are brilliant and will help stop it happenning again.

hope this helps