the filling loop valves should be across the valve body, if pressure is dropping this usually indicates you have a leak on the system, possibly a leaking radiator valve or a fractured pipe joint. if it is discharging water outside from pressure relief pipe it could be pressure relief valve itself thats not closing properly, this usually happens if the system has been over pressurised or it has over heated.
worse case the heat exchanger has fractured.if it in warranty ring ferroli
phil, January 2009