hi the pressure is to high on the boiler so it dripping water out the safety valve outside. this i s the reason for the drip. its also for the loud banging sound as when it throws water out and goes to close it has a spring which causes the sound. now what u need to do is first stop the pressure rising it either
1. u have left the filling loop open.
2. the filling loop is faulty and constantly letting water through.
3. there is a hole in the dhw heat exchanger causing the mains water to enter the central heating water.
there pressure should be around the 1.3 bar. fix the problem and every thing should be fine. u may need to change the driping valve if it keeps leaking after u have fixed the problem
kash, March 2013
