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Service pipes may be tested at the time of the foregoing test. However, the testing of service pipes may be completed as a separate operation ftom the main testing and, if so, the hyaro-static test pressure shall be 100 psi. The leak test shall be perfonned visually at the time of installation and there -shall be no leaks. 304.2 ELECTRICAL CONDUCTIVITY TEST . The CONTRACTOR S:1all perfonn a conductivity test within one week on completion of pressure testing or the main on all iron pipe watennains to establish that electrical thawing may be carried out in the future. Conductivity testing must be carried out in the ENGINEER's presence and approval before acceptance. The system (pipeline, valves, fittings and hydrants) shall be tested for electrical continuity and current capacity. The electrical test shall be made after the hydrostatic .pressure test and while the line is at nonnal operation pressure. Backfilling shall have been completed. The line may be tested in section of convenient length as approved by the ENGINEER. .Direct current of350 amperes 11+1110%, shall be passed through the pipeline for five minutes. Current flow through the pipe shall be measured continuously on a suitable - ammeter and shall remain steady without interruption or excessive fluctuation throughout the five minute test period. Insufficient current or h1tennittent current or arcing, indicated by large fluctuation of the ammeter needle, shall ~e evidence of defective contact in the pipe line. The cause shall be isolated and correctp.d. Thereafter, the section in which the defective test occurred shall be retested as a udtand shall meet the requirements. Sources of D.C. for these tests may be motor generators, batteries, arc welding machines, etc. D.C. arc. welding machines will probably be the usual source. These machines are available in adequate capacity for these tests and are equipped with controls for regulating the current output. All such equipment shall be furnished by the CONTRACTOR, subject to the approval of the ENGINEER. Cables from the power source to the section of system under test should .be of sufficient size to carry the test current without overheating or excessive voltage drop. Usable - sizes will probably be in the range of2l0 to 4/0 A W.G. Connections for the test shall be made at hydrants. The hydrants shall be in the open position with the caps ~.~ during the test. The cable shall be clamped to the top operating nut. :', NOTE: After the tes~.. the hydrant shall be shut off and- a cap loosened to allow hydrant drainage. Tighten cap after drainage. A hook-on type D.C. a.TJlII1eter placed on one of the cables leading to the hydrant is a converiient method of measuring current. 300-16