my boiler keeps loosing pressure and going to 0 there is no leak in the house and no water coming out the pipe outside has? had the had the expansion vessel sorted with more air please help

Mike, November 2017

The pressure has to be going somewhere

Check for leaks ALL ROUND the system:

Radiators
Valves
Pipework
Inside the boiler - the diverter valve may be weeping. Look for evidence on horizontal surfaces inside the boiler housing.

You may even have a leaking heat exchanger.

htrwhtrws, November 2017