Prevents backflow or back pressure of water between washing machines and tumble dryers. When a washing machine and a condenser or heat pump dryer are connected to a siphon connection, wastewater from one machine could be pumped into the other machine. A check valve in the wastewater line prevents this backflow or back pressure. Suitable for drain hoses with an inner diameter of up to 10 mm. Comes with 2 hose clamps (10 - 16 mm). Consumer note: Simply cut the drain hose of the appliance at the desired point or install a separate drain hose at the siphon. Insert the check valve and hose clamps between the two hose ends, ensuring that the embossed arrow points towards the siphon. Tighten the hose clamps securely. For wastewater only.