Engineering Design Manual - Loudoun Water

Chapter 6: Reclaimed Water
5. Adjoining developments and system-wide demands must be included in the model.
6. Identify model assumptions, including water source and calculated demands based on the
number of units and type of units in the development.
7. Include a node report showing elevation, demand, hydraulic grade line (HGL), and
pressure. A pipe report showing diameter, flow, velocity, length, and head loss must also
be included.
8. Write a conclusion of the model results identifying the nodes with the lowest pressure
during the various scenarios.
6.3 Reclaimed Waterline Layout
A. Plan View
1. Insofar as practicable, reclaimed water distribution systems developed for local areas
shall be compatible with Loudoun Water’s plan for an integrated water reuse system for
Loudoun County. Loudoun Water is developing a system of transmission and secondary
pipes from which the local components of the reclaimed water distribution system will be
supplied. Reclaimed water distribution pipes will be laid on a loop or grid system with
primary grids of 16-inch diameter at approximately 1 mile intervals. Secondary loops and
cross mains of smaller diameter shall be spaced not more than 1,000 feet apart with no
dead end length exceeding 500 feet.
2. As determined appropriate by Loudoun Water, mains shall be extended to the limits of
areas under development, so that adjacent areas and properties may be served.
3. Any relocation of existing water pipes and appurtenances due to development is the
responsibility of the Developer.
4. Reclaimed water pipe (and associated land disturbance) shall be located outside of very
steep slope areas in accordance with Section 5-1508 and other pertinent sections of the
most recent Loudoun County Zoning Ordinance.
5. Fittings and blockings should not be placed atop other utilities to avoid placement in
disturbed ground.
6. All pipes, branches and dead ends shall be equipped with blow-off valves and/or flushing
hydrants of adequate size and number to develop a velocity in the pipe of at least 2.5 feet
per second.
7. All dead end pipes over 5 feet in length shall be terminated in accordance with R-3,
TERMINUS BY FLUSHING HYDRANT; or R-4, TEMPORARY TERMINUS BY BLOW-
OFF of the Standard Details. A flushing hydrant is typically required. At Loudoun
Water’s discretion, a blow-off may be specified, where the subsequent extension is
considered certain.
Engineering Design Manual
September 2010 77