(a) General Provisions. The following Design Criteria are summarized herein to establish practical, uniform design of water distribution systems for the City. These criteria cover design factors and provides guidelines for evaluation of plans and specifications by the political subdivision having jurisdiction over the review of plans and specifications. These Design Criteria are also intended to conform to the construction standards and drawings for water systems and the regulations of the OEPA.
(b) Basis of Design. The basis of design for water distribution systems shall be the Hazen-Williams Equation, an empirical formula for estimating pipe flow:
V = 1.318CR 0.63 S 0.54
V = Velocity in feet per second
C = Roughness Coefficient
R = Hydraulic Radius (pipe diameter in feet for pipes flowing full) in feet
S = Head loss per unit length of pipe
Distribution systems shall be designed for the estimated maximum day rate of flow, or the fire flow plus the estimated average day rate of flow, whichever is more demanding.
(c) Minimum Pressure. The minimum allowable pressure in the water distribution system, at times of no fires, shall be 50 pounds per square inch in all mains. The minimum fire flow for design purposes shall be 600 gallons per minute at a residual pressure of 20 pounds per square inch.
(d) Maximum Velocity. The maximum velocity of the water in the system shall be 10 feet per second.
(e) Water Mains. The value of C to be used in the Hazen-Williams Equation shall be C=140. The minimum size of water mains shall be 8 inches in diameter. Dead-ending mains shall be minimized by looping of all mains. Where dead-ends occur, they should be provided with a fire hydrant for flushing purposes.
The minimum depth of water mains shall be 4 feet 6 inches from the top of the pipe to the finished grade elevation. The maximum depth of water mains shall be 5 feet and 6 inches from the top of the main to the finished grade elevation, except where utilities must be underpassed or as directed by the City.
(f) Water Service Lines. The value of C to be used in the Hazen-Williams Equation shall be C = 130. The minimum diameter of service lines shall be 3/4 inch, unless the distance from the main to the meter exceeds 120 feet, where the minimum service line diameter shall be 1 inch. Table 8.1 lists required minimum service sizes as determined by residential population. Fire hydrant services shall have a minimum diameter of 6 inches, but shall be no larger than the water main. For services larger than 2 inches, a tapping sleeve and valve must be installed. Table 8.2 shows the maximum size of service taps allowed for various sizes of water mains.
TABLE 8.1
MINIMUM SIZE – WATER SERVICES AND METERS
RESIDENTIAL AREAS
No. of Families | Service Size (inches) | Meter Size (inches) |
1 | 3/4 | 5/8 x 3/4 |
2-5 | 1 | 1 |
6-8 | 1-1/2 | 1 1/2 |
9-12 | 2 | 1 1/2 |
13-20 | 2 | 2 |
21-50 | 4 | 3 |
51-115 | 4 | 4 |
TABLE 8.2
MAXIMUM SIZE - WATER SERVICE TAPS
Pipe diameter (inches) |
6 |
8 |
10 |
12 |
Tap sizes (inches) |
1 |
1-1/4 |
1-1/2 |
2 |
The minimum depth of service lines shall be 3 feet and 6 inches from the top of the line to the finished grade elevation. The maximum depth of service lines shall be 5 feet from the top of the line to the finished grade elevation, except where utilities must be underpassed.
A curb stop and curb box shall be installed between the curb and sidewalk or between the walk and right-of-way line where there is not a curb lawn for each house and apartment unit unless otherwise approved the City. The curb stop box shall be plumbed and centered over the curb stop and shall be free of debris. House service installations shall conform to the Standard Drawings.
(g) Restraining and Concrete Blocking for Water Mains. All water main bends of more than 5 degrees shall be securely blocked against movement by using concrete blocking placed against undisturbed earth. Dimensions and quantities of blocking shall be as shown on the Standard Drawings. All mechanical bends, tees, etc. shall be restrained using mechanical restraining joints.
(h) Fire Hydrants. Fire hydrants shall be placed at all intersections and never more than 400 feet apart in Residential areas, and no more than 300 feet apart in Industrial or Commercial areas.
Fire hydrants shall be installed with a break flange located approximately 2 inches above the ground level to protect against flooding in case of impact to hydrant. Fire hydrants shall be consistent with the Standard Drawings.
A valve must be installed on all fire hydrant service lines. All connections between the main and the hydrant shall be restrained by anchoring pipe, tie bolts, or retainer glands.
(i) Meter Installation. Meter installation for individual services shall be consistent with the Standard Drawings. Table 8.3 lists required meter sizes as determined by Maximum Flow Demand for Commercial-Industrial applications. Meters must be installed prior to connecting the service to the main and before service starts. No common meters will be approved. All meters must have remote readers.
TABLE 8.3
METER SIZE FOR COMMERCIAL-INDUSTRIAL APPLICATIONS
Maximum Flow Demand (GPM) | Meter Size (inches) |
20 |
5/8 x 3/4 |
30 |
3/4 |
50 |
1 |
100 |
1 1/2 |
160 |
2 |
320 |
3 |
500 |
4 |
1000 |
6 |
(j) Valves. Valves shall be located at all branches of cross and tee intersections and at intervals not to exceed 800 feet in residential districts and 500 feet in commercial and industrial districts.
(k) Backflow Prevention. All commercial, industrial, and other OEPA required users shall provide adequate backflow prevention between the public water system and the customer’s system. These devices shall be approved by OEPA and the City prior to installation. These devices shall be tested and inspected annually. These devices shall be repaired or replaced if they do not meet the testing requirements. An annual report shall be submitted to the City detailing the testing procedures and results. Backflow devices shall be reduced pressure-zone type.
(l) Railroad and Highway Crossings. When boring is required, the casing pipe shall be designed to meet the requirements of the authority having jurisdiction and in compliance with the City of Urbana Construction Standards and Drawings. The size of the casing pipe shall be at least 4 inches greater than the largest outside diameter of the sewer pipe, joints, or couplings.
(Ord. 4206. Passed 1-24-06.)