A grit removal system for a hollow, completely enclosed emergency water reservoir tank employs a mobile suction head located within the enclosed tank, a flexible suction line coupled between the mobile suction head and the tank outlet, and a particle filtration unit located externally of the tank. The tank has an inlet from a municipal water supply system and an outlet leading to a local water distribution line. The tank is pressurized and maintained at an elevated pressure of preferably sixty to one hundred twenty psi relative to atmospheric ambient pressure. When the local water distribution line is opened, the pressure differential created due to the elevated pressure within the tank drives the mobile suction head so as to move it about the interior surface of the lower portion of the tank. The pressure differential between the interior of the tank and the local water distribution line forces water up through the suction head carrying entrained grit and sand with it. The water travels from the suction head through the flexible conduit, and through a filtration unit inlet conduit to a filtration unit. The filtration unit entraps sand and other grit, but allows the filtered water to proceed from the filter for use in a local water distribution line.