This Accumulator Tank is intended for installation in any pumped water system controlled by a pressure switch. The Accumulator Tank smooths water flow and reduces on/off cycling of the pump by lessening the variation in pressure and flow between the pump and the outlets in the system. The even flow of water gives better control of hot water temperature especially noticeable with instantaneous gas water heaters and with showers. The reduced on/off cycling reduces noise from the pump motor, and from shock pressures (pipe hammer). It also reduces battery drain, and gives longer pump life.