Johnson Pump Aqua Jet UNO Max 24V Water Pump The Aqua Jet Water Pressure system by Johnson pump features a five chamber positive displacement diaphragm pumps that are ideal for pressurizing water in a closed system like those in a boat or recreational vehicle. The integrated pressure switch automatically turns the pump on and off once the pre-defined pressure levels are reached. The self priming units feature a pump protector inlet strainer mounted on a stainless steel base. The quick connect ho