I have a pipe on the side of my house which is allways dripping water?

If its from the boiler then it will be the pressure relief pipe,its not standard practise to leave condensate discharge pipes open ended,they should be connected to a drain or a soak-away filled with lime chips.Check the gauge on the boiler it will probably be reading 3 bar,if it is then the filling loop is probably open.If it isn't then the pressure relief valve is probably ping water and needs to be replaced.