Water Demand
Water is essential to life as we know it. We can survive for weeks without food, but for just a few days without water.
Municipal water providers, even in communities as small as a few thousand inhabitants, deliver potable water to our homes for just a few dollars per thousand gallons. Because it is inexpensive and seems abundant, we are profligate in its use. A typical Pennsylvania family consumes between 50 and 60 gallons of water per person each day. (In State College, daily consumption of 40 gallons per person is somewhat below average. In some areas of the United States, average daily consumption is nearly 200 gallons per person.)
Although water providers take great care to ensure that the water they provide is potable, most of us actually drink less than one gallon a day. What do we do with the other 39 gallons? The State College Borough Water Authority estimates that 60% of the potable water we use serves only for the mechanical transport of waste.
Table 1. Domestic water use in the State College area. The average domestic water use per Equivalent Dwelling Unit (EDU)
is 140 gallons per day (GPD) and the average water use is 40 GPD/person.
The Point of Entry
Although tens of thousands of gallons of water are delivered to our houses each year, most homeowners know little about where it comes from and how it gets there. Many owners don’t know where it enters their house.
We use parts of the water system inside our home every day: the toilet or sink and appliances like the dishwasher or laundry machine. But others, like the shut-off valve, water meter with a bridging wire or ‘jumper’, and possibly a ‘back-flow preventer’ are less familiar (Photo 1).
Photo 1: A typical water supply arrangement in a household showing the shut-off valve on the water supply line,
the water meter, and the bridging wire.
Homeowners should know (many do not) the location of the shut-off valve and be prepared to turn off the water in case of a major water leak! The water meter, located close to the shutoff valve contains a pinwheel that is turned by water flowing through the pipe into the house. It is connected to small dials that record the volume of water delivered and may transmit the data to a reader outside the house. The meter enables the water provider to distribute the cost of water service among its customers and it can help the owner to detect water leaks inside the house.
The bridging wire should not be disturbed. It ensures that the electrical system in the house is safely grounded. If it is loose or disconnected, an electrician should be called.
Because household water might be contaminated accidently by a malfunctioning garden sprayer, dishwasher or other equipment, water flowing back into the water mains could contaminate the public water supply. A back-flow preventer keeps this from happening and is often required by the local plumbing code.
The pipe that actually brings water to the house, called a ‘service line’, belongs to the homeowner and must be maintained by him. Where it connects to the water main (usually at the street), there is a second shut-off valve called a ‘curb stop’ that is accessible only to the water provider.
The Distribution System
To deliver water to its customers, the water provider has installed and maintains a distribution system of pipes, pumps, elevated tanks and hydrants. At the heart of the system are tens of miles of pipes up to two feet in diameter called ‘water mains’. They are buried in the ground (below the frost line, where necessary) and form multiple loops, with valves and interconnections that allow any section of the system be isolated for maintenance or repair without interrupting service to the rest of the system. Regularly spaced hydrants provide water for fighting fires and allow periodic flushing of the mains. Elevated tanks with a capacity of a million gallons or more ensure adequate water pressure and flow during times of peak demand. The tanks and hydrants are the only elements of the water distribution system ordinarily visible to the public. The hydrant color may identify the water provider, and the color of the cap sometimes advises firemen of the available water pressure. It is not unusual to see elevated spherical tanks painted with the name of the host municipality, the water provider, or even decorated to resemble a giant peach, a basket of apples or even a basketball!
Treatment Plant
The water mains originate at the water treatment plant. Although the building may house administrative offices, a testing laboratory or maintenance facility, its primary role is to treat ‘raw’ water to make it safe and palatable to drink (Photo 2). Federal, state and local regulations set maximum contaminant levels (MCL) allowable in drinking water. ‘Polished water’ distributed by the provider must not contain any of the regulated contaminants in concentration greater than the corresponding MCL. Most providers try to achieve levels well below the mandated MCL.
Photo 2: The State College Borough Water Authority facility on West Branch Road, College Township.
Generally, the first treatment step is to draw the raw water through a filter of fine sand or diatomaceous ‘earth’ to remove suspended solids, bacteria and other microorganisms. Where needed, the filter may include a layer of odor-absorbing charcoal. The water is then subjected to chemical and biological processes designed specifically to remove each regulated contaminant. Where authorized by local regulations, fluorine may be added to protect children’s teeth. Before being pumped into the distribution system, the ‘polished’ water is disinfected with chlorine or by exposure to intense ultra-violet light or both.
Each year, water providers send customers “Water Quality Reports” showing results of periodic tests for the regulated contaminants.
“Hard” water (containing dissolved limestone) however burdensome, is not a regulated contaminant and ‘hardness’ is not ordinarily included in these reports.
Robert Schmalz is a retired professor of geology at Penn State. His special interests lie in the field of water chemistry. He served for many years as a member and as Chairman of the State College Borough Water Authority.
For more information, consult your local water authority.