we have a leak from the back of the boiler its not off the flow or return pipe but a fitting that comes of the boiler with a male threaded coupler of this is a nut with a spring inside. the nut has an 8mm hole drilled through it. theres nothing in the manual about this bit. can anyone help me as to what this is thank you

guy, January 2009

Sounds like a safety valve not now an installation requirement, drain down and remove generally 1/2 inch BSP size plug would suffice

a, January 2009