ORONGORONGO MAIN

Dominion, Volume 19, Issue 257, 14 July 1926, Page 3

ORONGORONGO MAIN

TESTING THE JOINTS THE FINAL TIGHTENING It was disclosed at the last meeting of the Hutt County Council that the staff of the city waterworks and drainage engineer had been very busy exposing the water-mains that were recently laid from the Orongorongo stream into the Hutt Valley and on to Wellington, and the county engineer, in reply to questions, stated that the excavation work which had been gotn on along the pipe line was occasions bv the testing operations that were bi ing carried out. When this maty was referred to him yesterday, the Cit waterworks engineer, (Mr. J. M. Mot ice) said that it was very ttecesscr that these steel lock-bar pine joint should be thoroughly tested befor they were subjected to the full pres sure that would be placed on then when the time came to turn on _ th< new supply. Mr Morice explain?' that hitherto the pipes used to brim water into town from Wainui or Karor were made of cast iron, which wernot asked to stand nearlv the pressure (or weight ot water) that would be placed on the Orongorongo main. The new main took in its supply from e height of 600 feet above sea level, whereas the altitude of the new dam at Wainui was 471 feet, the old dam at Wainui, 420 feet; the old reservoir at Karori, 463 feet; and the new reservoir at Karori, 579 feet above sea level. The proposal was that the water from the intake at Oroneorongo should flow by direct main into the lower dam at Karori on. gravity. It would be too much to ask it to flow into the top dam at Karori, as there was too little difference in the height above sea level to ensure a lively flow, so the emergency basin would be the lower dam at Karori, which would be kept full, so as to give a direct fall to the citv mains and also the. suburban districts un to its own height or thereabouts. The calculated pressure on the lower levels, coming across Lower Hutt and Petone would be 3461b5. to the square inch. Such a pressure could not be withstood by the old cast-iron mains, the joints of which were plugged bv molten lead. Such a form of joint could never be applied to the lattcr-dav steel mains, which are clamned together ■ with the aid. of a stout iron collar that pressed into a rubber band. When it was suggested that rubber was a substance liable to perish, .Mr. Morice said that aw.iv from the light and to a great extent immune from sudden changes of temperature rubber had a fairlv long life. There were manv water-main joints on the market to-dav, but nearlv all of them provided for a rubber-clamped joint. . It was always known that the first tightening of the joints would not lie the final one before the water was admitted but it was not considered wise to Have the trenches open in certain nlaces, and it was because they now had to act at each joint for the final tightening that the mains had to be exposed once more.