Stop the transparent flow of water that falls from your tap to the drain and follow it back through the pipes under your sink, under your house to an intricate maze of cast iron and PVC piping, all adding up to 150 miles of water mains.
Whether it’s appealing to the palate or not, tap water is a constant and a commodity. We use it every day, from pasta to the dog’s water, but where our water comes from is a mystery to most of us.
The city of San Luis Obipso has a multi-source water supply from the Salinas Reservoir, more commonly known as Santa Margarita Lake and Whale Rock Reservoir in Cayucos. Santa Margarita Lake supplies the majority of the water for the city, while Whale Rock is more of a back-up.
Dean Furukawa, San Luis Obispo Water Treatment plant supervisor, says the city will soon be tapping into Lake Nacimiento as well.
Much of the state relies on groundwater, which makes the city of San Luis Obispo lucky to have the three water sources says Furukawa. Water from lakes and streams (water above ground) requires more treatment to meet state and federal standards.
“It’s unique for a water system to have one source, let alone three sources,” Furukawa said.
Nacimiento Lake has been available for water use since 1959. The Nacimiento Water Supply Project will utilize 50 plus miles of pipeline to supply water to 18 agencies and cities. The project is to plan for future expansion and to have a back-up source for drought years explains Sam Vigil, environmental engineering professor at Cal Poly.
The last time the city experienced a severe drought was the late 1980s, which was also the last time the city had to resort to pumping ground water says Vigil. Furukawa says there were conservation measures put in place for water rationing and water use restrictions.
According to the city of San Luis Obispo Utilities Department there are 13,500 metered customers needing a constant supply of uninterrupted potable water. Geographically this area makes for a complicated distribution system of pipes, valves and tanks.
There are two types of pipeline that run under the city: transmission mains and distribution mains. The larger transmission mains pump water from one end of the city to the other, while the smaller distribution mains are sending water to each property. The city is in the process of replacing older pipes, many of which are over 100 years old. According to the Utilities Department, the life expectancy for the pipelines is 50 years meaning the city has to replace 2 percent of the system infrastructure each year.
The water starts at the water treatment plant in Stenner Canyon, then goes to transfer pumps that increase the pressure and send it throughout the northeast end of the city. About half the water flows by gravity and half is pumped to a storage reservoir flowing out via gravity and pressure reducing valves (PRVs). This system is used to deliver water at the right pressure attempting to use as little electrical power as possible.
The treatment plant uses ozonation, a process that kills bacteria through the infusion of ozone. Ozone is a strong disinfectant, but because it doesn’t remain in the water very long, chlorine is still used to keep the water clean in the pipes. Flouride has also been added to the San Luis Obispo city water since 1954. The chlorine is used to keep the water clean in the pipes. There are 10 water storage facilities in the city for times of high demand and fires. They have a combined storage of 24.21 million gallons.
The difficulties lie in maintenance and design of distributions system to keep a consistent flow of potable water. Engineers are working to develop news techniques and systems.
“They’ve started uses long cylindrical bags … that act like a condom on the inside of the pipe,” said Wayne Campbell, civil engineering senior. “It conforms to the pipe to keep the water from leaking. It’s a cheap way to keep old pipes in use.”
Campbell said as far as design engineers are making connections between pipes flexible to prevent breakage. He also said that better materials are being used like switching from cast iron to PVC pipes since PVC doesn’t corrode like iron or cause a metallic taste in your mouth.
Some residents complain about the taste of the city’s tap water. It’s easy to grab a bottle of water with the Alpine ice-cap designed label off the shelf, but some engineers and tap water enthusiasts argue that the water from the tap is the only way to go.
“I think it’s bogus,” Vigil said. “Tap water is EPA (Environmental Protection Agency) regulated, whereas bottled water is not. It’s a matter of personal taste. A Brita filter will take the taste out … activated carbon takes away chlorine.”
The Safe Drinking Water Act (SDWA) passed by Congress in 1974 authorizes the U.S. EPA to set national health-based standards for drinking water. Bottled water companies often are not held to these same standards and go through their own treatment processes.
“It’s not this magical, mythical source of water,” Furukawa said about bottled water. “A lot of the time what people purchase in the bottles is just reprocessed tap water. We deliver pennies on the gallon verses dollars on the gallon in bottles.”
Nicole Swabey, a biological sciences senior at Cal Poly says she uses well-water in Los Osos and drives to get five-gallon jugs for her drinking water. She says she used to drink the San Luis Obispo tap water all the time when she lived in town.
“I don’t think it’s necessary,” Swabey said about bottled water. “Most places have free water and it really doesn’t taste all that much different.”