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Fire Hydrant and Water Main Valve Inspections and Maintenance

Unidirectional Flushing Print E-mail

Water distribution systems require a care and maintenance program to extend their life expectancy.

So let's discuss one very important component of the annual water system maintenance management program - system flushing, or in our terms, Unidirectional Flushing.  Check out the interactive flash demonstration of unidirectional flushing below.

Objectives of Water System Flushing

For best results, the operational status of the distribution network must be known. Before a Unidirectional Flushing program can be developed, one must have a clear picture of how the system works, and be able to feel the pulse of the system.

That is why a complete diagnosis of the system and its components is recommended before initiating and developing a Unidirectional Flushing program.

A diagnosis involves an assessment of the conditions of the components of the water distribution system based on the system’s operating goals of adequacy, dependability and efficiency of water utilization. A diagnosis involves four basic components of study of the system to evaluate its status:

  1. A mechanical assessment, whereby every fire hydrant, isolation valve and water main valve is inspected for deficiencies and evaluated for flushing purposes and manipulated for ease of use.
  2. A hydraulic assessment, whereby hydrant/pressure tests are taken at each hydrant in order to identify hydraulic weaknesses caused by leakage, shut valves, etc.
  3. Leakage assessment, using the acoustic amplifier as a first step, is performed at each hydrant and valve thereby localizing possible leaks in the system. The correlator is used later only at the pre-identified sectors where leaks have been detected.
  4. Water quality aesthetics are evaluated at each fire hydrant, for color and odor problems, and at the same time purging stagnant water out of the hydrant pipe leads.

Unidirectional Flushing is recommended for health reasons as well. The process discharges dead non-potable water from the system, which is then replaced with water containing chlorine to better disinfect the system.

Objectives of Water System Flushing

Water system flushing is an annual maintenance program recommended by the National Fire Code, and strongly recommended by the Ontario Ministry of the Environment and Energy’s “Drinking Water Objectives”. “System Flushing” is the process of discharging dirty water and debris that has accumulated in the pipe since the last time flushing was implemented.

Unidirectional Flushing of the water distribution network is the systematic removal of non-solidified deposits using optimum water velocity. Strategic control and operation of hydrants and valves ensures that the water used to clean always comes from previously flushed sections, with minimal disturbance to surrounding areas.

The purpose of Unidirectional Flushing is to ensure proper pipe cleaning by controlling the direction of water flow to the designated flow hydrant using the main valves to utilize the greatest water velocity available in the system.

Therefore it is necessary to know the system’s performance and its operational configuration. Are any valves closed or partially closed? Are there any minor or major leaks? Do all the hydrants and valves work? Are there any reducers, or inaccuracies or discrepancies with the system drawings? Etc.


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