- Prevents water back-flow between washing machines and laundry driers ,- If a washing machine and a condensing or heat pump dryer is connected to a single siphon connection, the waste water could be pumped from one machine to the other ,- A non-return valve in the waste water pipe prevents this backflow ,- Suitable for drain hoses with an inner diameter of up to 10 mm , ,Note for Consumers: ,The direction of flow on the valve must be noted, since if it is inserted the wrong way round the flow of water will not be stopped! ,Only suitable for waste water. - Material: Metal ,- Diameter: 10 mm ,- Suitable for: Down Pipe Tube 2 years legal warranty only