Many manufacturers suggest in their instructions to empty the water butt in winter and leave the tap open.
The reason for this is that water in the water butt freezes and expands and this could fracture or split your water butt.
If you’re lucky enough to live in a place where it doesn’t freeze then you could leave it running all year round but it might affect your guarantee if it does get a crack.
Some people have suggested placing a ball at the top of the water butt and they reckon the ball will push against the ball instead of the butt, but we cannot guarantee this will work.
Some of our larger water butts and tanks have outlets at the bottom which are ideal to use for draining.