DC Water and Sewer Authority

DCWASA Design Guideline for Development Projects within the District of Columbia

DCWASA is providing these general guidelines to help the designers of projects to be constructed within the District of Columbia. DCWASA sells a pipeline design manual, with standard details and specifications, which contains information for the design and construction of water mains, connections and sewers within the city.

Minimum Drawing Requirements
- All submitted drawings must be in CAD format, preferably AutoCAD.
- Drawing sheets to be no larger than 24" x 36" if possible. If larger than 24" x 36", half scale drawings shall be included with the submittal for review.
- Use Engineers scale for civil drawings. Architects scale may be use for structural details.
- All fittings needed to make connection shall be noted including station or location.
1. Background Drawing Must Show
  1. North arrow
  2. Labeled property and lot lines, water/sewer easements where applicable
  3. Square number, lot number, address of project
  4. Street names with the quadrant
  5. Curbs (dimensioned) and labeled
  6. All utilities (dimensioned) including vaults to scale (plot outside dimensions)
  7. Manholes, valves, trees, etc
  8. Plot of lawge sewes/water mains must include thickness
  9. Sewers noted in feet and inches are concrete and/or brick masonary, constructed in place, i.e. 3'6", 4'0". These should be labed, as feet and inches, not just inches
  10. Water mains noted as "OD" are steel and the size should be noted as OD
  11. Existing water and sewer connections to be removed from the public system for all buildings to be demolished
  12. Applicable WASA standard construction notes
2. Submittals Required (Addition to Drawings)
  
  The following items are required to be submitted at the time of review:
  1. Required water flow data for fire and domestic
  2. Booster pump calculations
  3. Storm and sanitary flow data, including storm water management calculations
  4. Any letter requesting approval for exceptions to WASA policy
Design Criteria for Connections to Public System
- General
  1. Separate fire and domestic water connections required
  2. Separate storm and sanitary sewer connections required
  3. No connections permitted in driveway alignment
  4. Tie-in dimensions in 2 directions must be provided for all connections
  5. No alley connections permitted
  6. Profiles must be provided for all connections, sewer and water
  7. No connections permitted within drip line of trees
  8. All connections must be perpendicular from sewer or water main to property line
  9. All fittings neede to make connection to sewer or water main shall be noted
  10. WASA Standard Details may be referred to instead of including drawing
- Water
  1. All connections (3-inch and larger) must have a shut-off valve in a casing per detail W/20.01
  2. The minimum size water connection valve on 3 and 4 inch connections in public space shall be 6-inch
  3. All 2-inch and smaller water services must be installed per detail W/80.01
  4. No 2-inch water service taps will be allowed into 3-inch,4-inch, or 6-inch water mains. Two-inch connections must be made into a cap or plug on tell installed for the service
  5. All fire services must have water meters
  6. Water main taps larger than 2-inch will only be approved if the applicant makes a request in writing
  7. Water meters can be inside of a building if the applicant makes a request in writing
  8. No connections will be allowed to 16-inch or larger water mains unless the applicant makes a request in writing and they meet the DCWASA requirements of installing a main line valve on each side of this valve
  9. No fire service connections will be allowed to 6-inch mains when a fire pump will be installed within the building with a pumping capacity greater than 500 gallons per minute
  10. Fire hydrant flow test must conducted for a building that will have a fire service 3-inch and larger
- Sewer
  1. All sewer connections must have profiles shown on the plans. The profile must have invert elevations at the connection point to the public sewer and where it leaves the building. This connection point in a manhole on a sanitary connection cannot be lower than the top of the existing sewer
  2. All sewer connections must have a clean-out or clean-out manhole at the property line. Invert and top elevations must be provided at the clean out or manhole. 8" and smaller diameter require cleanout, larger than 8" require manhole
  3. No sanitary sewer connections will be allowed to combined sewers if separate storm sewers are available to the property
Design Criteria for Water, Storm, and Sanitary Sewer Extensions or New Subdivisions
1. General
  1. All WASA utilities shall be designed, if possible, parallel to property line, right of way or easement lines
  2. All standard details used shall be WASA Standard Details and can be referred to by the WASA Std. Detail number. In cases where WASA has no detail contact WASA design manager.
  3. Standard alignment is as follows:
  4. Service water main = 2' north or east of centerline street or front block of sidewalk
  5. Service Sanitary sewer = 2' south or west of centerline street or back block of sidewalk
  6. Storm sewer = 10' either side of center line of street (if less than 5' from curb, 5' off curb)
  7. Any water main alignment change shall be accomplished with standard bends
  8. Any sewer alignment change shall be accomplished in manhole
  9. Any replacement WASA utility shall be designed as close as possible to the existing utility unless approved otherwise by WASA
  10. Stationing shall be as follows
  11. Water main shall be continuous, 0+00 at left or bottom of sheet, left to right direction. All tees, main line valves, bends, fittings etc. shall be stationed
  12. Sewers shall be continuous, beginning to end (not manhole to manhole), at the centerline of manhole with 0+00 being at low point discharge manhole. All manholes, wye branches, bends etc. shall be stationed
  13. If possible, the water main stationing shall be tied-in with property lines each block
2. Sewer
  
  The size of the public sewers shall be as follows:
  - Service sanitary = Minimum 10"
  - Storm = Minimum 15"
  - Basin connection = 15"
  Sewer and manhole spacing shall be as follows:
  - 10" - 27" sewers = 400' or less
  - 30" and larger sewers = minimum 400' or as necessary
  The nominal depth shall be as follows:
  - Service sanitary = 10.5' below approved grade to invert
  - Storm sewer = 5.5' of cover below approved grade
  Material shall be as follows:
  - Service sanitary = 10" - 24", PVC, SDR 35
  - Storm = RCPR (Reinforced Concrete with Rubber Gasket), minimum Class III
  - Combined = RCPR (Reinforced Concrete with Rubber Gasket)
  - Manholes = Pre-cast, brick, cast in place base
  A profile showing all crossing utilities is required for all sewers, storm, and sanitary including building connections
3. Water Main
  1. Size of service water main is minimum eight-inch (8") diameter
  2. The main shall be valved for a minimum of one block shutoff
  3. Fire hydrants shall be placed at a minimum spacing of 400' apart. The fire hydrant lead shall be 6" diameter
  4. A water main profile is normally not required for 8" and 12" mains unless it is being constructed in an unimproved area. In new sub-divisions a street grade profile is required
  5. Service water main shall be ductile iron with restrained joints
4. Profiles
  1. The direction of profile shall be oriented to match plan.
  2. The horizontal scale shall be the same as the plan. The preferred vertical scale is
  3. 1" =10', 1"=5'
  4. Plot all crossing utilities
  5. Plot gradient line
  6. Provide invert elevations at all sewer manholes, incoming and outgoing pipes unless grade is straight through manhole where one elevation is acceptable
  7. Where pipes of different sizes enter a manhole keep tops of sewers together as much as possible to maintain nominal depth
  8. If the difference between incoming and outgoing pipes in a sanitary sewer manhole is greater than 2.5' an outside drop is required

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