A valve formed from a frustoconical piece of foldable material, having folds extending from a closable end towards the other end that connects to a container of liquid, each fold having an inner crease extending into the interior region of the nozzle. The valve has a biasing mechanism that may include a spiral spring encircling a nozzle to bias the inner creases inward to cause them to abut each other at the closable end so that the valve is maintained in a closed position. When liquid is forced into the interior region under sufficient pressure it causes the nozzle to move from the closed position to an open position so liquid flows from the interior region out the closable end of the nozzle, and when the pressure on the liquid is removed, the biasing mechanism causes the nozzle to move back to the closed position.