Firstly this drip is from the safety valve which should lift at approx 3.5bar so if your gauge indicates this pressure then lower the system by venting from the nearest rad vent v/v.Lower pressure to 1 bar observe this pressure when running boiler. Obviously if the gauge indicates much less than 3.5 bar then your s/v is lifting light and needs replacing. However if your system pressure keeps rising without you putting in top-up water and again lifts your s/v there could be problems on the domestic hot water heat exchanger leaking cold water at mains pressure into your CH system.Ensure that the top-up v/v is shut also.
Guytawe, May 2010
