16mm flow value/inline tap. Can be used at the end of the line to give you the ability to drain a system or can be used in pumped systems to even out pressure or control flow. The Autopot Red Flow Control Tap is a 16mm barbed tap connection made to be used with 16mm inner diameter piping to stop or allow the flow of water or nutrient solution through your pipework. Ideal for stopping the flow of water to enable easy tank changes.