first im not a plumber but i like to do what i can about a year or so i took a radiator out of my bathroom so that i could fit a corner bath i am now refitting the radiator in my little workshop the problem i have come across is this i did not keep the input connection to the top of the radiator . i have tried a 22mm to 15mm reducer because the pipes are all 15mm the 22mm connection is to big. the nut on the rad will not go on the threads of the 22mm connection does anyone know what size the connection is likely to be , connection has to be slightly smaller than the 22mm i have no idea what year the oil fired central heating was fitted need help as its all ready except for this connection thanks for your help