Newsletter - November 1999
Waterline freeze prevention appliance for
service line bleeding
Every area of Canada, without exception, is faced with the possibility of no water
because of our climate. Each year water mains and service lines freeze. Depending on the
severity of winter temperatures, the problem varies from region to region. Many
municipalities located in northerly or Pre-Cambrian Shield regions experience peak water
consumption from December through May. This can be explained by the practice of bleeding
water for waterline freeze prevention.
There is now a promising new way to discontinue service line bleeding of potable water,
thereby reducing the waste and the costs of treated drinking water attributed to water
bleeding.
Water lines are protected routinely from freezing by maintaining a continuous flow of
water through the lines. This is achieved by discharging large quantities of clean,
treated potable water through orifices, devices or taps in residential or commercial
outlets, off-line hydrants, and dead-end mains into the sewage system.
In Canada, bleeders such as taps left partially flowing, the bent arm on the float of
toilets preventing reservoirs from filling, and petcocks hooked up to sewer lines
contribute to a tremendous waste of treated water. A single bleeder can waste more water
in a two-month period than an average sized family should use in an entire year.
Water bleeding creates a need for larger water treatment and sewage treatment plants.
This, in turn, necessitates larger water distribution and sewage collection systems and
their components such as mains, reservoirs, lagoons and pumps to handle the larger flows
that are generated. It causes higher capital, operations and maintenance costs, including
manpower, chemicals and electricity.
Bleeding generates larger quantities of wastewater that is colder and diluted. It
adversely affects physical, chemical and biological sewage treatment processes. In
addition, bleeding reduces water distribution system pressure. It gives a false sense of
security to consumers who believe that water is available in unlimited quantities, leading
to little or no conservation of treated water.
Waste continues into the summer months when bleeding is not required to prevent
freeze-up of water mains and service lines.
Alternatives to bleeding include heat-traced water lines, installation of
freeze-prevention appliances, and installation of dual lines for re-circulation. New
systems must be designed and constructed for the worst weather conditions by installing
pipes below the frost line and/or insulating them. As freeze-ups occur, they may be
excavated and repaired. Heat tracing, re-circulating and the lowering of water lines are
expensive alternatives to install and operate in existing systems. Freeze-up repairs are
expensive, an inconvenience, and a temporary solution.
A re-circulating system for small municipalities might be a viable solution. It could
require looping, or interconnecting water mains, and the installation of strategically
located valves to direct flows for re-circulation back to the clear well in the water
treatment plant.
A remedy for service line bleeding is to install a waterline freeze prevention
appliance. The unit works on the principles of bleed, capture and return.
Water is bled into a holding tank at a controlled rate from the municipal supply
through an orifice. When the tank is filled, a pneumatic switch is tripped and the pump,
and motor, pump the water back into the water main. Depending on the water pressure, each
cycle consists of a 30 to 45 minute filling period followed by a four minute pump
down-cycle. Water in the service line is kept in constant motion and freezing is
prevented. The unit acts as a temporary bleeder in case of an electrical or mechanical
failure. When the malfunction is rectified, the unit resumes its normal cycle.
The appliance is easily installed indoors in new or old houses. Initial purchase price
and installation costs are low, approximately $1,000. Eliminating a bleeder by using a
waterline freeze prevention appliance could result in a one-year payback on the purchase
and installation costs.
Condensed from a paper by Simon Miazga, Mi-Sask Industries Limited, 510 - 50th St.,
Saskatoon, SK, S7K 6L9, March, 1999.
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