how can i fix it?

You don't say what type of boiler you have, is it a combination boiler? What is the make and model?

To increase the pressure you normally just need to boost the amount of water from the mains using the filing loop attached to your boiler for a few seconds until you see the dial shows the approriate pressure then turn this off again.

That should be all you need to do - without knowing what type of boiler you are talking about it is impossible to give you any more detailed information, sorry.

agent4927
November 2013