I have had a service engineer out to my boiler and he has given me a warning notice to say that because the PRV pipework is run from the boiler to outside in speedfit pipe and connectors it is at risk of melting in the event of a blowout and should be only installed in copper ? I believe that as speedfit is used extensively in central heating systems the exact same stresses and temperatures would apply throughout the heating system as would apply to the PRV pipework at the point of blowdown and therefore I believe there is no risk,can anyone help ?