why is my Worcester Bosch combi boiler losing ressure all the time the heat?

sounds like faulty exp vess and possibly dumping water out prv

steve
December 2007

I am assuming you mean water pressure.
When you top the system pressure up when cold does it lose that pressure before you put the heating on? If not then it sounds like the expansion vessel has gone if it does then you have a leak somewhere

Pip
December 2007