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Thermal Expansion
(.pdf)
The
Town of Friday Harbor works hard to insure that
the water we deliver to our customers meets or exceeds all health standards.
All public water systems are required to
develop and implement cross-connection control (CCC) programs. The requirements
are contained in WAC 246-290-490 of the Drinking Water Regulations.
The purpose of which is to protect water
quality by preventing the backflow of water from the customers plumbing into the
public water system. You are receiving this letter because our records indicate
that you have or are about to install a backflow prevention device in your
system.
When
a backflow prevention device is placed on a water service line, the water that
has been delivered to the customer's facility is prevented from returning
through the meter to the water main. This creates a closed loop system within
the customer's building.
This letter and
enclosed brochure are being sent to you via certified mail to ensure that you
receive this important information regarding the potential dangers of thermal
expansion in a closed system.
Thermal Expansion is a condition that exists whenever water is heated. The
heated water cannot expand into the public water system because of the backflow
device in your system. Therefore, pressure may build up in your water heater
tank and household plumbing. The resulting pressure buildup or thermal expansion
usually causes the pressure relief valve (T & P Valve) on your water heater to
open and water is emitted from the drain piping of your water heater. Under
certain conditions, such as a failure of the T&P valve, a water tank may
explode. Please read the attached brochure for additional information.
If
you notice a discharge of water from your water heater you are probably
experiencing thermal expansion. Current plumbing codes require the installation
of thermal expansion relief devices in "closed systems". The two most common
methods are to install either an expansion tank, or a thermal device installed
on the cold water line to the tank. We suggest you discuss the best solution for
your needs with a licensed plumber.
Thank
you for your understanding as we continue to meet or exceed all regulatory
requirements in providing clean, safe drinking water to all of our customers. It
is our pleasure to serve you.
11/28/2005
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