Backflow questions answered -

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What is backflow?

Under normal conditions, water from the your local water agency
flows into your premise. When backflow occurs, water flows
from your premise back into the distribution system
(or from an isolated system, such as a boiler, into the consumer’s
distribution system). If that water is contaminated, it can carry
pollutants into the distribution system, which can cause illness
or even death.

What is a backflow preventer?
Backflow preventers are mechanical plumbing devices installed in a plumbing system to prevent water from flowing backward in the system. A properly installed, tested and maintained backflow preventer at the service entrance to a building or property can reliably prevent the backflow of water of an unknown quality from flowing back into the community water system. Thus keeping everyone's water safe.

Why do I have multiple backflow preventers on my property?
Living in the Truckee-Tahoe area it's a hard task to put a backflow
preventer out by your water meter. The chance of freeze or a snowplow taking the device out could cost the customer a lot of time & money. Some water districts let you isolate certain cross connection hazards within your property. This can be but not limited to Fire suppression systems, irrigation, boiler systems and wells. This way your plumber will be able to locate the backflow preventer inside and out of the elements. So if you have any of the systems mentioned above you may need more than 1 backflow preventer.

How does backflow occur?
Backflow into the public water distribution system can occur when the
water pressure in the consumer’s premises is higher than the pressure
in the water distribution system. This condition can be caused by a
drop in water pressure in the distribution system (for example,
because of firefighting or a break in a water main) or by the presence
of systems within a consumer’s premises that operate at higher
pressures than that of the distribution system (for example,
commercial boilers or steam heating systems).

What does a backflow preventer look like?
Here are a few examples of what backflow preventers look like.

How backflow might happen
Picture of an RP, DC, PVB

Why do I have to pay for and install the backflow preventer? Why doesn't my water company pay the bill?
The backflow preventer is installed to protect the public water supply against possible hazards in your plumbing system. The actual or potential cross connection belongs to the property owner and not to regulatory officials or the water utility. Once the water goes beyond the meter, water quality could be altered. The water utility does not want the water back, nor do the water customers want to purchase used water. If a backflow preventer is required to keep the water safe, then the person who created the cross connection (actual or potential) shall purchase, install and maintain the backflow preventer.

Why do I have to have my backflow device tested every year?
By testing your backflow device annually it's more likely to be
functioning properly. Backflow preventers are mechanical units
that have internal seals, springs, and moving parts that are
subject to fouling, wear, or fatigue. The annual test ensures
a properly functioning device, and certifies that the device has
not been removed or had a by-pass line installed around it.

What is a Cross Connection?
Any pipe, valve, fixture, etc., in a drinking water plumbing system that may allow the drinking water within the system to become contaminated or questionable in quality. Cross connections can either be eliminated or protected by an air gap or mechanical backflow preventer.

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