Test tank
Hi Tora,
A water Butt on this side of the pond is a receptacle for waste water, such as that draining off a roof. In days of yore, a wooden barrel was used, that's what my grandmother had, but these days a plastic creation, sort of oil drum shape, takes it's place. Hope that's clear.
Nerys
When the winds before the rain, soon you may make sail again, but when the rain's before the wind, tops'l sheets and halyards mind