Oak barrel water butt - which tap ?

Normally barrel users (e.g. publicans) would use a wooden spigot hammered into the hole. But you could try metal if you preferred. I think you'd have to make up something long enough to go through the wood, like a piece of 1/2 inch galvanised water pipe threaded each end or along its length, with a nut each side of the wood and a tap screwed onto the end. Or a socket screwed onto the end and a tap screwed into that - depending on whether you prefer male or female.

Normal taps are not always very good for low pressure set-ups like this because the tap washer tends to adhere to the seat and isn't easily forced off by the low water pressure. So you'd want to choose some form of gate valve.

Rob Graham