(A) Once constructed, all sanitary sewers and manholes shall be watertight and free from leakage. The rate of infiltration, into the sanitary sewer system between any two adjacent manholes or the entire system shall not be in excess of 100 gallons per inch of pipe diameter per mile per day (100 gpd/in/mi). The contractor shall be required to repair all visible leaks to the satisfaction of the town, even if the infiltration requirements are met.
(B) Any leakage found during the infiltration test shall be corrected by the contractor at his or her expense. The method of repair shall be approved by the town. Grouting of the joint or crack to repair the leakage shall not be permitted. If the defective portion of the sanitary sewer cannot be located, the contractor shall remove and reconstruct as much of the work as necessary to obtain a system that passes infiltration requirements.
(C) All gravity sanitary sewers constructed of flexible pipe (PVC and HDPE) shall be mandrel tested no sooner than 30 days after installation in accordance with these standards.
(D) The contractor shall bear the complete cost and supply all equipment necessary to perform the required tests.
(E) All tests shall be conducted under the observation of the town’s inspector. It shall be the contractor’s responsibility to schedule testing with the inspector.
(1) Low pressure air test. All gravity sanitary sewers shall be tested for infiltration by means of a low pressure air test as generally described herein. Alternate infiltration tests will only be allowed upon written approval by the town.
(a) Equipment.
1. The contractor shall be responsible for providing all equipment and supplies necessary to perform a low pressure air test including but not limited to the following:
A. Mechanical or pneumatic plugs;
B. Air control panel;
C. Shut-off valve, pressure regulative valve, pressure relief valve and input pressure gauge. The pressure regulator or relief valve set shall be set no higher than 10 psig to avoid over pressurization; and
D. Continuous monitoring pressure gauge having a range of 0 to at least 10 psi. The gauge shall be no less than four inches in diameter with minimum divisions of 0.10 psi and an accuracy of
±
0.04 psi.
2. To reduce the potential for sewer line over-pressurization, two separate hoses shall be used. One hose will connect the control panel to the sealed line for introducing low pressure air. The other will be used for constant monitoring of air pressure buildup in the line.
3. If pneumatic plugs are utilized, a separate hose shall be required to inflate the plugs.
A. Ground water level. The ground water level shall be determined by excavation by the contractor.
B. Air pressure adjustment. The air pressure correction, which must be added to the 3.5 psig normal test starting pressure, shall be calculated by dividing the average vertical height, in feet of groundwater above the invert of the sewer pipe to be tested, by 2.31. The result gives the air pressure correction in pounds per square inch to be added. The allowable pressure drop of 1.0 psig (or 0.5 psig) and the minimum time periods are given in Table A or Table B.
C. Maximum test pressure. In no case should the stalling test pressure exceed 9.0 psig. If the average vertical height of groundwater above the pipe invert is more than 12.7 feet, the section so submerged may be tested using 9.0 psig as the starting test pressure. The 9 psig limit is intended to further ensure workman safety and falls within the range of the pressure monitoring gauges normally used.
(b) Test procedure. The following are general procedures to be employed in the performance of the test. Test data sheets shall be submitted to the town.
1. Plug installation and testing.
A. After a segment of pipe has been backfilled to final grade, prepared for testing, and the specified waiting period has elapsed, the plugs shall be securely placed in the line at the ends of each segment to be tested.
B. Seal test all plugs before use. Seal testing may be accomplished by laying one length of pipe on the ground and sealing it at both ends with the plugs to be checked. The sealed pipe should be pressurized to 9 psig. The plugs shall hold against this pressure without bracing and without any movement of the plugs out of the pipe. No persons shall be allowed in the direct line of the pipe while the plugs are tested.
C. Plug the upstream end of the line first to prevent any upstream water from collecting in the test line. This is particularly important in high groundwater situations.
D. When plugs are being placed, the pipe adjacent to the manhole shall be visually inspected to detect any evidence of shear in the pipe due to differential settlement between the pipe and the manhole. A probable point of leakage is at the junction of the manhole and the pipe. This fault may be covered by the pipe plug, and thus not revealed by the air test.
2. Line pressurization. Low pressure air shall be slowly introduced into the sealed line until the internal air pressure reaches 4.0 psig greater than the average back pressure of any groundwater above the pipe, but not greater than 9.0 psig.
3. Pressure stabilization. After a constant pressure of 4.0 psig (greater than the average groundwater back pressure) is reached, the air supply shall be throttled to maintain that internal pressure for at least two minutes. This time permits the temperature of the entering air to equalize with the temperature of the pipe wall.
4. Timing pressure loss.
A. When temperatures have been equalized and the pressure stabilized at 4.0 psig (greater than the average groundwater back pressure), the air hose from the control panel to the air supply shall be shut off or disconnected. The continuous monitoring pressure gauge shall then be observed while the pressure is decreased to no less than 3.5 psig (greater than the average back pressure of any groundwater over the pipe). At a reading of 3.5 psig, or any convenient observed pressure reading between 3.5 psig and 4.0 psig (greater than the average groundwater back pressure), timing shall commence with a stop watch or other timing device that is at least 99.8% accurate.
B. A predetermined required time for a specified pressure drop shall be used to determine the line’s acceptability. Traditionally, a pressure drop of 1.0 psig has been specified. However, other pressure drop values may be specified, provided that the required holding times are adjusted accordingly.
C. If the specified pressure drop is 0.5 psig rather than the more traditional 1.0 psig, the required test times for a 1.0 psig pressure drop must be halved. Specifying a 0.5 psig pressure drop is desirable in that it can reduce the time needed to accomplish the air test without sacrificing test integrity. Therefore, the following subsections contain provisions for both the traditional 1.0 psig pressure drop and the more efficient 0.5 psig drop, which is given in parentheses.
5. Determination of line acceptance. If the time shown in Table A or Table B, for the designated pipe size and length elapses before the air pressure drops 1.0 psig (or 0.5 psig), the section undergoing the test shall be deemed to have passed and shall be presumed to be free of defects. The test may be discontinued once the prescribed time has elapsed even though the 1.0 psig (or 0.5 psig) drop has not occurred.
6. Determination of line failure. If the pressure drops 1.0 psig (or 0.5 psig) before the appropriate time shown in Table A or Table B has elapsed, the air loss rate shall be considered excessive and the section of pipe shall be determined to have failed the test.
(c) Test times.
1. Test time criteria. The Ramseier test time criteria requires that no test section shall be accepted if it loses more than “Q” cubic feet per minute per square foot of internal pipe surface area for any portion containing less than 625 square feet internal pipe surface area. The total leakage from any test section shall not exceed 625Q cubic feet per minute.
2. Allowable air loss rate. A Q value of 0.0015 cubic feet per minute per square foot shall be utilized to assure the owner of quality pipe materials, good workmanship and tight joints.
3. Test time calculation.
A. All test times shall be calculated using Ramseier’s equation:
T = (0.085) (D * K)/Q
Where:
T = Shortest time, in seconds, allowed for the air pressure to drop 1.0 psig
K = 0.000419 DL, but not less than 1.0
Q = 0.0015 cubic feet/minute/square feet of internal surface
D = Nominal pipe diameter in inches
L = Length of pipe being tested in feet
B. For more efficient testing of long test sections and/or sections of larger diameter pipes, a timed pressure drop of 0.5 psig may be used in lieu of the 3.0 psig timed pressure drop. If a 0.5 psig pressure drop is used, the appropriate required test times shall be exactly half as long as it is obtained using Ramseier’s equation for “T” cited above.
(2) Mandrel test for select pipe.
(a) A 5% “GO-NO-GO” mandrel deflection test shall be performed on all HDPE and PVC gravity sanitary sewer pipes.
(b) The mandrel test shall be conducted with a rigid device sized to pass 5% or less deflection (or deformation) of the base inside diameter of the pipe. The test shall be conducted no earlier than 30 days after reaching final trench backfill grade, provided that, in the opinion of the town, sufficient water densification or rainfall has occurred to thoroughly settle the soil throughout the entire trench depth. If, in the opinion of the town, densification has not been achieved within the 30-day time frame, the mandrel size shall be increased to measure a deflection limit of 3%.
(c) The mandrel (GO-NO-GO) device shall be cylindrical in shape and constructed with nine or ten evenly spaced arms or prongs. Mandrels with less than the required arms shall not be allowed. The mandrel diameter dimension “D” shall be equal to the inside diameter of the sanitary sewer. Allowances for pipe wall thickness tolerances or ovality (from heat, shipping, poor production and the like) shall not be deducted from the “D” dimension but shall be counted as part of the 5% or less deflection allowance. Each pipe material or type required to be mandrel tested shall be tested with a mandrel approved by the pipe manufacturer, while meeting the requirements of this chapter. The “D” mandrel dimension shall carry a tolerance of ± 0.01 inches.
(d) The mandrel shall be hand pulled through all sewer lines. Any section of sewer not passing the mandrel shall be uncovered, replaced or repaired to the town’s satisfaction and then retested.
(e) The contact length (L) shall be measured between points of contact on the mandrel aim. The length shall not be less than that shown in Table C.
(f) The contractor shall provide proving rings to check the mandrel. Drawings of mandrels with complete dimensions shall be furnished by the contractor to the town upon request for each diameter and specification of pipe.
(Ord. 2019-8-26(A), passed 8-26-2019)