A model or make of boiler would help to enable a suitable reply as some boilers have built in top-up systems, these still need manual setting but the device is normally accessable underneath the boiler and involves turning a key or inserting a tool which comes with the boiler, the operation proceedure being part of the installers hand over to the house owner.
Other boilers have an external filling loop which is connected from the cold water house supply to the central heating return pipework again this pipewok is identified under the boiler at the valve set usually in diagram form.This loop should consist of a braided hose approx 30mm long with two inline valves and a non-return valve to conform to Water Regs. Open the valve off the cold water pipework using a screwdriver set slot in-line with valve body,the other valve nearest to return pipework should have a blue tap open this to put water into your boiler and observe gauge set it 1 to 1.5 bar. Shut off both valves on completion excess pressure can the vented off at any radiator vent.Regarding the cold water feed if you have a combi this pipe will continue to your boiler, if you have a system or heat only boiler this pipe usually terminates at the filling loop, it is unusual to find a filling loop away from the boiler but is possible if you have an additional expansion vessel .
Guytawe
May 2010
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