An open-flow helium cryostat for single-crystal X-ray diffraction experiments capable of reaching 14 K has been developed using off-the-shelf components. Solid/liquid air build-up is prevented using the transfer-line helium back-flow and a heated nozzle. The system has run for over 30 h with no frost build-up. The effectiveness of the system has been demonstrated using test data for oxalic acid, terbium vanadate and dysprosium vanadate.