§ 82-492. Sewer.

(a)

Pipe specifications. The following are minimum specifications for sewer pipes:

Pipe
Minimum	Eight-inch laterals
	Six-inch house services
Minimum cover	Four feet
Minimum grade	Eight-inch pipe	0.40 percent
	Six-inch pipe	0.65 percent

 

(b)

Material. The following are minimum specifications for materials used in sewer construction:

(1)

Pipe. Pipes shall be constructed of the following:

a.

Polyvinyl chloride: ASTM 3034 classifications SDR 35.

b.

Ductile iron: Push-on joint class 350.

(2)

Manholes. Manholes shall be precast as per ASTM C478 with the following specifications:

a.

Four-foot inside diameter.

b.

Five-inch wall thickness.

c.

Plastic steps with three-eighths-inch rebar.

d.

Cast-iron manhole frame and cover.

1.

Inside roadway 460#.

2.

Outside roadways 360#.

(c)

Construction. Sewers to be laid in graded ditch on good material (rock or other unsatisfactory material shall be removed and good material brought in as required). Pipe shall be bedded in select material (good bank material, clay or crushed stone) well compacted. Backfill should continue with the same material, using hand tools, up to six inches above the top of the pipe. The balance of the backfill may be ditch material, providing it does not contain any large rock particles.

(d)

House service connections. In general, house service connections shall incline upward approximately 45 degrees above a horizontal line normal to the direction of flow in the street main. Service lines shall be laid on a straight line and grade from the sewer or riser to the property line and in no event shall service lines be less than 3½ feet deep to invert of the pipe at the property line. Where required, short radius bends shall be used to connect the service branch to the house service line. Pipe service connections together with bends, shall be placed on a compacted bed of crushed stone in such a manner as to be self-supporting and to relieve the strain on branches and bends.

(1)

Risers. Where trench depths are such that risers are required, service lines shall be installed by excavating into ditch bank and installing riser in a vertical position against undisturbed earth, and the entire length of the pipe containing the riser encased in concrete. Risers shall extend to the heights directed and shall be encased in a Sonotube fibre form as manufactured by Sonoco Productions Company or a brick masonry stack. Bends shall be used to connect the riser to the house service lines.

(2)

Stoppers, caps and plugs. All house service connections shall be closed with factory manufactured pipe stopper of such design and secured in such a manner as to not leak under a maximum hydrostatic head of ten feet or five psi air pressure. The pipe stopper shall be able to be removed without special tools, excessive force or breakage of the pipe bell.

(e)

Deflection testing for PVC pipe. The maximum deflection in the installed PVC pipeline shall not exceed five percent of the pipes original internal diameter. Deflection testing will be required using either a deflectometer or a "Go-no-go" mandrel. Portions of the project shall be randomly selected to be deflection tested. Such portions shall consist of not less than five percent of the total reaches (reach being length of pipe between two manholes) in the project (excluding house leads). Where deflection is found to be in excess of five percent of the original pipe diameter, the line shall be excavated to the point of excess deflection and carefully compacted and around the point where excess deflection was found. The line shall then be retested for deflection. However, should after the initial testing the deflected pipe fail to return to the original size (inside diameter) the line shall be replaced. In the event that deflection occurs beyond the five percent limit in any section of five percent or more of the reaches tested, the entire system shall be tested.

(f)

Testing. On completion of each block or section of sewer, sewer shall be cleaned, tested and inspected. All repairs shown necessary by the inspection shall be made. Broken or cracked pipe shall be replaced; defective joints, if any, replaced; all deposits removed, pavement replaced; and AC sewer left true to line and grade, entirely clean, free from lumps or producing jointing materials, etc., and ready for use. Each section of sewer between manholes. shall show, upon examination from either end, a reasonably full circle of light. The allowable limit of groundwater infiltration for any one or more sections of sewer with any type joint allowable under these specifications (all sizes), shall not exceed 100 gallons per 24 hours per mile of sewer line per inch of diameter. Any line that does not meet this specification will be rejected and must be repaired. No infiltration tests will be made until normal infiltration conditions are established. Tests shall be made before existing sewers are connected and measured by means of a V-notch weir. These tests will be conducted over a period of time sufficient to determine the correct rate of groundwater infiltration. When infiltration occurs in excess of the specified amount as hereinabove given, defective pipe or joints shall be located and repaired. If the defective portions cannot be located as much of the original work as necessary to obtain a sewer within the allowable infiltration limits upon retesting shall be removed and reconstructed.

(1)

Exfiltration test. When lines are above the groundwater table, an exfiltration test may be required. For this test, the line shall be filled with water under a minimum head of two feet above the top of the outlet pipe of the upper manhole and the level maintained through the test. The rate of exfiltration shall not exceed the allowable rate for infiltration, except that an allowance of an additional ten percent of gallonage shall be permitted for each two feet of head over the basic two feet minimum head. When the leakage exceeds the specified amount, satisfactory corrections shall be made.

(2)

Low-pressure air test. Where sewer grades are such that preclude performance of the ex-filtration test, a low-pressure air test shall be conducted on each section of sewer after completion and before acceptance. Prior to air testing, the section of sewer between manholes shall be thoroughly cleaned and wetted. Immediately after cleaning or while the pipe is water soaked the sewer shall be tested with low-pressure air. Sewers may be tested in lengths between manholes or in short sections (25 feet or less) using Air-Lock balls pulled through the line from manhole to manhole. Air shall be slowly supplied to the plugged sewer section until internal air pressure reaches approximately 4.0 psi. After this pressure is reached and the pressure allowed to stabilize (approximately two to five minutes), the pressure may be reduced to 3.5 psi before starting the tests. If a 1.0 psi drop does not occur within the test time, then the line has passed the test. If the pressure drops more than 1.0 psi during the test time the line is presumed to have failed the test, and it will be required to locate the failure, make necessary repairs and retest the line. Minimum test time for various pipe sizes, in accordance with ASTM C828, as amended to date, is as follows:

Nominal Pipe Size (inches)	T(time) Min/100 (feet)
4	0.3
6	0.7
8	1.2
10	1.5
12	1.8
15	2.1
18	2.4
24	3.6

 

Required test equipment includes: Air-Lock balls, air hose, air source, timer, rotometer as applicable, cutoff valves, pressure reducing valve, 0-15 pressure gauge; 0-5 pressure gauge with gradations of 0.1 psi accuracy of plus or equal to two percent. Keep records of all tests made. Copy of such records will be given to the owner. Such records shall show date, line number and stations, operator and such other pertinent information as required by the owner. Observe proper safety precautions in performance of the air testing. It is imperative that plugs be properly secured and that care be exercised in their removal. Every precaution shall be taken to avoid the possibility of over pressurizing the sewer line.

(3)

Repairs. All visible leaks shall be repaired regardless of whether infiltration, ex-filtration or air test is within allowable limits. No sewer will be accepted until leakage tests demonstrate compliance with one of the above leakage test methods.

(Code 1979, ch. 47, § I)