Abstract: A pumping system for use in a self-service car wash for supplying liquid at a high or low-pressure having a pump in communication with a liquid applicator and in communication with a first liquid supply. A second liquid supply is in communication with an inlet portion of the pump through a supply valve which selectively permits liquid to be drawn from one of the liquid supplies. A by-pass mechanism, in communication with the pump, is provided to reduce the pressure of the liquid supplied from the pump to the liquid applicator. A control mechanism is connected to the supply valve and the by-pass mechanism whereby when the control mechanism is activated the supply valve and the by-pass mechanism are actuated and liquid from the second liquid supply is supplied to the liquid applicator at a pressure lower than liquid supplied from the first liquid supply.