A low-cost turbine flowmeter has been designed for studies of water thermosyphoning. It was built from an ordinary medical 'spinhaler' inhalent impeller and was capable of measuring flows down to 1.7 ml s^-1. It caused a pressure loss of 5 mm head of water (50 Pa) at a flow of 20 ml s^-1, but the smallest detectable flow was then 10 ml s^-1. The device could be manufactured in a small workshop without difficulty.