My boiler is about 12 years old and I have to refill the pressure on a very regular basis(every few days). What causes this and do I need to replace boiler? I have no OBVIOUS signs of a water leak in the house!! The hot water thermostat has stopped working, is this connected to the loss of pressure??
Thank you (from a lady who has even less of an idea about boilers than cars!!!!!!)

Clare, October 2007

When you add water to the system you must as a minimum bleed the radiators,until water comes out,start with the lowest and farthest away from the boiler,and keep an eye on the boiler pressure,it needs to be about 1.25 bar.Also your expansion vessel may need recharging(to 1 bar).Not really something you should try yourself ,try topping up and bleeding system for now and see how you get on

Graeme Smith, October 2007