Engineering Design Manual - Loudoun Water

Chapter 4: Water Distribution
detention time, thereby promoting water quality. Single supplies will be considered in
need of reinforcement when serving 40 homes or 4 commercial establishments.
b. The maximum length of permanent dead-end water pipes is 500 feet. Where possible,
water pipes shall be looped to eliminate dead ends, promote better water quality, and
increase fire protection.
2. The maximum curvature by joint deflection for water pipes equal to or less than 12-inch
diameter is a 300 foot radius arc (3.5 degrees/joint with 18 foot pipe sections). For pipes
larger than 12 inches, the maximum curvature by deflection is a 500 foot radius arc.
When restrained joint pipe is specified, consult manufactures recommendations for
maximum joint deflection.
3. Fittings and blockings should not be placed atop other utilities to avoid placement in
disturbed ground.
4. Water pipes (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 Loudoun
County Zoning Ordinance.
5. Any relocation of existing water facilities due to development is the responsibility of the
Developer. Where grading is to occur, resulting cover on existing water pipe must remain
above design minimum and may be considered excessive if adding more than 4 feet.
Encumbrance of pipes for future access and/or re-excavation will necessitate replacement
in kind, in the form of a parallel facility.
6. Separation
a. Provide a minimum 10 foot horizontal separation (outside to outside) with sanitary
sewers, including manholes.
b. Provide a minimum 6 foot horizontal separation (outside to outside) with storm
drainage structures.
c. Provide a minimum 15 foot horizontal separation to a building or other above-ground
structure.
7. Street Design
a. In public right of way, placement must be in accordance with current requirements of
the Virginia Department of Transportation.
b. Along divided roads water pipes will be located outside the ultimate right-of-way.
c. Along undivided roads, water pipes will be allowed under the pavement, a minimum 5
feet from the outside edge of pavement or gutter pan (7 feet from the face of standard
curb and gutter). Where the pavement width is 24 feet or less, 3 foot horizontal
separation from the gutter pan is permitted, if needed to attain separation from sanitary
sewer. Generally centerline of water pipe should be located 8 feet off the centerline of
Engineering Design Manual
September 2010 35