What is causing my Optimax HE 31c to lose water pressure F37?

Hi my optimax he 31c is losing water pressure, f37. This has happened numerous times now after refilling pressure to 1 bar within 2 hours it has gone again. I have also noticed my condenstae pump is running a lot more often every 18 mins, is it possible for the water to get into this line? how do i stop it? thanks.