D3 Prep Water storage

Purpose of water storage

• equalizing supply and demand

• Increased operating convenience

• Balancing pumping requirements

• decreasing power costs

• emergency and fire requirments

• surge relief

• increased chlorine contact time

• Blending water from different sources

Match Supply with Demand

The demand for water changes throughout the day and night by having sufficient water storage, the wells and water treatment plant can operate at a consistent rate to meet the daily water requirements during high demand, water is taken from the reservoirs. During minimum demand the reservoirs are filled in preparation for the next day. frequent cycling of distribution system pumps is an indication of inadequate storage capacity.

Convenience

Is a system has sufficient water storage, it is possible to produce enough water for a 24hr period by running the water treatment plant 1-2 shifts each day. Water storage also allows flexibility with maintenance activities that take the treatment plants or wells offline for a period of time during the maintenance activity

Balance Pumping Requirements

Elevated storage facilities can utilize the head gained by the elevation to provide water to systems without the need to cycle on additional booster pumps as system demands increases. Systems without elevated storage must cycles pumps to meet system demand and cannot benefit from gravitational water flow.

Lower power costs

Water storage provides operational flexibility which in turn allows a system to take advantage of special electrical rate structures. Most power companies will offer lower electrical cost for power usage during off-peak times Therefore reservoirs can be filled during off-peak times at lower cost.

Emergency Storage

There may be times when the sources is not available or wells providing water to the system suddenly fail. During times such as these, having adequate water storage will allow the utility to continue to provide service to its customers, Elevated storage will provide water even if system booster pumps have failed

Fire Requirements

One of the major purposes of distribution system water storage is to ensure there is an adequate supply of water to fight fires, fire flow water storage requirements generally accounts for about 50% of the system water storage capacity.

Surge relief

The cycling of booster pumps can generate large shock waves that travel throughout the system these waves result in water hammer which can damage system components, Elevated storage tanks that “float” on the system can help absorb the shock by allowing water to flow up its risers and into the tank.

Chlorine Contact time

Surface water treatment plants and groundwater requiring disinfection must provide adequate contact time between the chlorine and water before serving it to the public.

Reservoirs can provide this contact time before the water reaches the first customer

Blending

Systems that use both surface and groundwater, or water from multiple sources with varying water quality, use reservoirs to blend the water, this helps the system to deliver water of consistent quality to is customers.

Altitude valve

Valve that automatically stops water flow when water level in a storage tank reaches a predetermined level

Elevation Head

The amount of energy water possesses due to its elevation, measured in feet.

Cathodic Protection

A DC Electrical system for preventing corrosion of metal storage tanks and pipes

Sacrifical Anode

An easily corroded material deliberately installed in a pipe or tank. The intent is to sacrifice this anode to corrosion, while the water supply facilities remain relatively corrosion free. Inspected annually and should last around 10 years.

Calcium Hypochlorite

A solid form of chlorine used for storage tank and pipe disinfection. also called High Test hypochlorite. HTH

Sodium Hypochlorite

A liquid form of chlorine used for disinfection

piezometric Surface

A water level that is equal to the water level in hydraulically attached body of water. Used to see tank water level by using a sight glass attached t the side of the tank.

Pressure Surge

A sudden change in system pressure. Most often caused by a pump shutting down due to a loss of power.

Water Age

The length of time a particular volume of water has been in the distribution system.

• Lowest - Late evening

• Highest - Early morning

Water Hammer

The slam or shutter of a pipe (similar to acoustic shock waves) when a sudden change in water velocity occurs. Most often caused by a valve operating too quickly