Can a bolier fault drop pressure even if there isn't a leak on the system?

on condensing boilers the main heat exchanger can leak internally and the water will flow out with the condensate pipe and make it difficult to see where the leak is

Paul the Gasman
February 2010

does the system contain the appropriate level of inhibitor. if not corrosion may cause hydrogen formation inducing a drop in system pressure
what make and type of boiler do you have.
the checking of the pressure relief valve is a good idea.
the pressure gauge may also be faulty allowing over charging together with high temperature operation may cause the prv to operate causing low pressure when the system cools down

daver
February 2010

look outside at the PRV valve outlet,the copper elbow on the outside wall when the boiler is working wall maybe wet or rust stained . tie a plastic bag on the elbow leave it for an hr see if the bag now contains WATER .
(it should NOT)
check the boilers expansion vessel air pressure, may be flat or diaphram gone

wirecutterman
February 2010