Sulphur and carbon isotope studies of food webs

A drain valve device is provided adapted for draining liquid contaminant such as oil and/or water, collected from compressed air or other gas. The valve is closable by the gas pressure and loaded to open when the pressure sufficiently falls to permit the discharge of collected contaminant. The device incorporates a captive contaminant outlet tube separate from the valve and manually displaceable to operate and open the valve against the gas pressure. The tube may project from the valve casing sufficiently to enable it to be gripped and displaced to operate the valve without the risk of contaminant or compressed gas coming into contact with the operator's hand. An external drain pipe may be coupled to the tube and displaced from a remote position to operate the valve. The tube can be snapped into a captive position in relation to the valve casing while being axially displaceable relatively to the casing for operating the valve. The casing may comprise a skirt which is slotted and elastically expansible and provided with projections and a collar on the outlet tube can be forced past the projections to captivate the tube.