This device stops water syphoning back up the exhaust pipe into the engine. It should be sited so that the outlet pipe or non-return valve is at least 300mm (12in) above the waterline – essential if the point at which the water is injected into the exhaust is less than 150mm (6in) above the waterline. Anti-syphon devices are optional extras on many installations, but are worth the added expense because of the consequences of backflow.
