A cleaning system, suitable for chemically removing limescale from a plate heat exchanger, having at least one inlet (8a, 8b) and at least one outlet (13a, 13b), by contacting and reacting the limescale in the plate heat exchanger with an acidic solution (descaler, 3), the system comprising: - a first pressurisable container having: ▪ a descaler portion to accommodate descaler, and a gas portion to accommodate gas; ▪ a primer for pre-pressurising said first pressurisable container; and ▪ at least one first conduit (7a, 7b) for establishing a fluid connection between the descaler portion of said first pressurisable container and the inlet(s) (8a, 8b) on a plate heat exchanger; - a second pressurisable container having; ▪ at least one second conduit (12a, 12b) for establishing a fluid connection between the outlet(s) (13a, 13b) on the plate heat exchanger and said second pressurisable container; and ▪ a reaction product portion to accommodate reaction products, and a gas portion to accommodate reaction product gas; and - characterised by a third conduit comprising a valve: the third conduit positioned to establish a fluid connection between the gas portion of said second pressurisable container and the gas portion of said first pressurisable container so as to recycle reaction product gas to the gas portion of said first pressurisable container, and thereby repressurize said first pressurisable container; the valve restricting said fluid connection between said first and second pressurisable containers (2, 11). - a first pressurisable container having: ▪ a descaler portion to accommodate descaler, and a gas portion to accommodate gas; ▪ a primer for pre-pressurising said first pressurisable container; and ▪ at least one first conduit (7a, 7b) for establishing a fluid connection between the descaler portion of said first pressurisable container and the inlet(s) (8a, 8b) on a plate heat exchanger; ▪ a descaler portion to accommodate descaler, and a gas portion to accommodate gas; ▪ a primer for pre-pressurising said first pressurisable container; and ▪ at least one first conduit (7a, 7b) for establishing a fluid connection between the descaler portion of said first pressurisable container and the inlet(s) (8a, 8b) on a plate heat exchanger; - a second pressurisable container having; ▪ at least one second conduit (12a, 12b) for establishing a fluid connection between the outlet(s) (13a, 13b) on the plate heat exchanger and said second pressurisable container; and ▪ a reaction product portion to accommodate reaction products, and a gas portion to accommodate reaction product gas; and ▪ at least one second conduit (12a, 12b) for establishing a fluid connection between the outlet(s) (13a, 13b) on the plate heat exchanger and said second pressurisable container; and ▪ a reaction product portion to accommodate reaction products, and a gas portion to accommodate reaction product gas; - characterised by a third conduit comprising a valve: the third conduit positioned to establish a fluid connection between the gas portion of said second pressurisable container and the gas portion of said first pressurisable container so as to recycle reaction product gas to the gas portion of said first pressurisable container, and thereby repressurize said first pressurisable container; the valve restricting said fluid connection between said first and second pressurisable containers (2, 11). the third conduit positioned to establish a fluid connection between the gas portion of said second pressurisable container and the gas portion of said first pressurisable container so as to recycle reaction product gas to the gas portion of said first pressurisable container, and thereby repressurize said first pressurisable container; the valve restricting said fluid connection between said first and second pressurisable containers (2, 11).