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Questions and AnswersQ. If water is under pressure how can I have backflow?A. The water supply in our homes is normally under pressure, but occasions can arise when the pressure drops. For example, if there is a fire in your neighborhood and the fire department begins to pump large amounts of water; the water pressure in the surrounding area can drop. This low pressure or no pressure can contribute to conditions that allow water to flow backwards. If at the same time, a fixture in the house is open and submerged in water, water can be siphoned back into the water supply. Or if at the same time as the fire in the neighborhood, you were using a garden hose with a sprayer jar attached to the end of the hose filled with fertilizer, that fertilizer (or whatever was in the jar) could be sucked back into the household water supply. The next time water was drawn from a fixture inside the house that fertilizer would be in the water. This is the reason that modern plumbing codes require anti-siphon protection to be installed on the water lines that lead to garden hose connections. Q. My outside faucets are new and have vacuum breakers built in, are there other things I need to be concerned about in back flow protection?A. Yes, One area I have seen problems with is the toilet fill valve. The refill valves in many older toilets do not have built in anti-siphon protection, and it is possible for the water stored in a toilet tank without anti-siphon protection to be drawn back into the water supply. About the only time you'd even know this was happening is if you use a "toilet tank cleaner" that turns the water blue. Working as a repair plumber I would often shut the main water off in the house to perform a repair. I would open a faucet in the basement to remove the pressure and drain the water. The water draining out of the pipe would turn blue. The blue water in their toilet tank had been sucked back into the supply. Modern plumbing codes mandate the installation of anti-siphon toilet fill valves in all gravity flow toilets (new installations, retrofits, and replacements). However, it is not easy to determine if an existing refill valve in a toilet tank meets local plumbing codes; many of them are not marked with any identification. However, when you replace a refill valve, you should only purchase one that is clearly marked "anti-siphon" or carries a UPC shield showing the valve is "code-approved". Be aware it is possible to purchase a non code-approved valve. When in doubt, ask your plumber or hardware store for assistance. Just as important is to ensure the fill valve is of a correct height and the refill tube (small tube) maintains an air gap above the water level. Q. What is cross connection?A. A cross connection is a point in a plumbing system where the potable (pure, drinking water coming into the house) is connected to a non-potable source. A cross connection exists when the drinking water system is or could be connected to any non-potable source such as a plumbing fixture. Pollutants can enter the water system through uncontrolled cross connections when backflow occurs. There are two types of backflow: Backflow can occur due to siphoning if the pressure in the water supply suddenly drops to a low level. This can happen if the municipal water pumping system fails, a municipal water line breaks or when fire trucks pump from fire hydrants. In each of these cases, the pressure in the water supply lines may drop below atmospheric pressure as the lines drain, creating a vacuum which can pull water (and any pollutants or contaminants) from a garden hose and into the water supply lines. Backflow can occur due to back pressure if the pressure in a garden hose exceeds that in the supply pipeline. This can occur if pumps such as chemical injectors are connected to the garden hose. However, when injection pumps are used to inject chemicals into hoses or pipelines that are directly connected to municipal water supplies, hose connection vacuum breakers do not provide adequate protection of the water supply. Reduced pressure principle backflow prevention devices are the only acceptable backflow prevention devices when chemicals are injected into hoses or pipelines that are connected to municipal water supplies. Backflow due to back pressure can occur even when pumps are not used. For example, if a spray nozzle which can be shut off with a valve is used on the end of the garden hose, and that valve is closed but the faucet is left open, the pressure in the hose will equilibrate with the water supply pressure, and the hose will expand in response to the supply pressure. However, a sudden large water usage in the house or at another location can cause the supply pressure to drop. This will cause the hose to contract, forcing water from the hose back into the municipal supply. Pressure can also build up in a pressurized hose if air is trapped in the hose and then expands as it heats in the sun. This pressure buildup can force water from the hose backwards into the water supply pipelines. Hose connection vacuum breakers will prevent backflow from occurring from these sources by opening to relieve the pressure build-up as soon as the pressure in the hose becomes greater than the supply pressure. (UF/IFAS Hose Connection Vacuum Breakers for Backflow Protection http://edis.ifas.ufl.edu/AE079) Q. Are there examples of incidents of water contamination?A. Yes, plenty. I will list a few web sites that include examples.
http://www.crd.bc.ca/water/crossconnection/incidentsandevents.htm Q. I would like more information on different backflow protection devices, where do I look?A. There are many good informational sites, to list a few:
http://www.mclemoreservices.com/article2.html Q. Why is the City doing this program now?A. Frankly if not now, when? The need for a program has existed since the city began supplying water to its residences. The water department has always prided itself on maintaining clean water for city residences; they have strived to insure pure water is delivered in the distribution piping to each user. The plumbing inspection department has maintained strict enforcement of the plumbing code requirements for clean water, however things happen. Piping is changed without permits, fires break out, and people will do dumb things. The State of Michigan knows this and the Michigan Department of Environmental Quality has established rules that water purveyors (suppliers) have to establish programs to maintain water quality. This is the origins of the City of East Lansing Cross Connection Control Program and Ordinance No. 1135. Q. Will this be an ongoing program?A. Yes. Things change all the time. Businesses change or are remodeled. Homeowners are constantly changing and improving their property. Builders are constructing new houses and buildings all the time. Once the initial survey and inspections are completed the City will need to start all over again. Think of it like laundry, even if everything is clean and put away, tomorrow you will have the dirty clothes you are wearing today. |