A system (10) for providing a stream of water that includes a surfactant, comprising a source (14) of water, means (32) to cause water to flow along a water supply duct (34), and a venturi injector (36) within the water supply duct. The venturi injector (36) communicates with an inlet duct (77) to supply surfactant; and the system comprises a surfactant supply duct (80, 83) that communicates between the inlet duct (77) and a surfactant container (18), the surfactant supply duct comprising a first portion that incorporates an on/off valve (38) and a second portion (83) that incorporates a check valve (84) to control flow. A plurality of surfactant containers (18) may be connected to the inlet duct (77) in this way; and each surfactant container 18 may be mounted within an open-topped chamber (68) to which hot water may be provided to heat the contents of the surfactant container (18).