Flushing System Helps Authority Control Chlorine Residuals

The Clayton County Water Authority (CCWA) in Clayton County, GA, installed an automatic flushing system to help control chlorine residuals in its 1,253 miles of distribution mains. The project help stabilize chlorine residuals and also lowered labor and water costs for the authority, which produces 39 mgd of potable water and serves a population of 218,000.

During 2000 and 2001, CCWA installed eight Hydro-Guard® Direct Discharge automatic flushing units. Before installing the units, the authority's manual flushing program consumed 3,384,000 gallons per month. After installation, the gallons flushed dropped to 933,300 gallons per month. Between the water savings and labor savings, CCWA estimated its cost savings at more than $4,500 per month. On a per-unit basis, that represented a savings of more than $562 per month; meaning the units paid for themselves in less than five months.

The standard Hydro-Guard unit features an atmospheric discharge with an air-gap to prevent backflow. Once programmed, the unit's 9 volt lithium battery-powered controller opens and closes a solenoid-operated valve at the preset days, times and for the correct duration.

The standard units are constructed of non-corrosive weather-resistant materials and weigh approximately 46 pounds. They contain three main components. The control module houses the continuous loop, 14-day, 16-event, battery-operated programming pod, battery and built-in sample port. A hand-held programmer plugs into the programming pad to download the flushing schedule.

The mechanical module houses the discharge riser, flow/energy dissipater chamber, flow discharge chute and internal fastening devices. The buried base module houses a 2-inch nylon glass reinforced solenoid operated valve, sample connection and external splash plate.

The standard unit is installed onto a potable water line using a two-inch service connection. A two-part security system protects the unit from unauthorized access. The cap features security screws protecting the programming pad. Special security bolts are used on the unit's base. The standard unit is not intended for operation in freezing climates. However, an optional dewatering pump kit is available to winterize the units.

Hydro-Guard's direct discharge units, as installed by Clayton County, weigh approximately 100 pounds and can be connected to a sanitary or storm sewer. The units discharge through a brass Wilkins Zurn 975XL RPZ back-flow prevention valve. The discharge pipes are plain-end schedule 80 PVC piping.

The direct discharge units are available with a Thermal Control Valve for freezing environments. The valve monitors water temperature within the machine. When the water temperature reaches 40 degrees F, the valve opens to let water run through the machine. This cycling (approximately 1 gallon per minute) brings warm water from below ground into the unit. As the water temperature rises, the valve closes. The thermal control valve does not interfere with the programmed flushing cycle.