Hi, the pressure gauge on my boiler keeps dropping slowly overnight from 1 bar, with the temp gauge turned down to zero in the hallway. I turned all the rads off and increased the boiler pressure to 2 bar which I left overnight, again with the central heating gauge turned to zero in the hallway. with no drop in pressure the following morning. I reduced the boiler pressure back to 1 bar, and began opening one rad at a time nightly, again with the hall temp gauge on zero. my question, -- is there a way I can test for this pressure drop other than what I am trying?, as there are 16 rads, and I am unsure doing what I am will locate any leak etc`. I have tightened all fixtures and fittings with no water leak visible, is there an alternative way I can pressure test the system, the pressure drop only seems to occur when the temp gauge in the hallway is asking the boiler to heat the rads, is there a simpler solution ???. The boiler is a Worcester greenstar 30cdi, feeding a OSO unvented system, which incorporates both the domestic & Central heating system, Grateful for any constructive advise, Goafer.