Hi I have purchased the large in line filter and the ‘Tap for all Barrels’ SKU AP224 to go with the Rigid 47 litre Water tank. I shall connect the filter to the Tap and then into the 16mm hosepipe. I just need to know what diameter of hole do I need to drill in the tank to fit this Water Tap ??? I am assuming it should be 16mm, but I am not sure. I just do not want to make a silly mistake , which would be hard to rectify !! Thanks for your help ! Gary