Just tried to put some inhibitor into my combi boiler via the filling loop. Checked the connections and the only place the adaptor nut (that goes onto the can) would fit it just prior to the non-return valve (ie without using the actual loop). It went in fine, but when I tried to take the nut off the one way valve didn't seem to work and every where got sprayed with my can of X100!!! I managed to get the filling look back on but not before it had sprayed over the boiler plug and fuse, which has now short-circuited the system and the boiler now does not have power to it.
Where did I go wrong? I checked I was filling it in the direction of the arrow on the non-return valve, and I checked which pipe was which (ie cold water mains inlet and boiler loop). Did I just have a dodgy non-return valve, and if so I guess I need to drain the system to fit a new one.
jmh (covered in X100 inhibitor and not pleased with herself!!)