CITY WATER

New Zealand Herald, Volume LXXV, Issue 23160, 5 October 1938, Page 20

CITY WATER

# domestic services; RELINING v OF MAINS FLOW -'AND PRESSURE GAINS "Tests of city water mains to deterpressures and rate of flow, following the scraping and relining with cement of the pipes, are now being carried out in the Parnell area. Thi? work has been going on in various parts of ' the citj- and suburbs for the past two years, and the city waterworks engineer, Mr. A. D. Mead, has had tables prepared showing the results of the investigation. Generally the rate of flow in the residential areas, where relining has been clone, is now in'/.,.excess ■ qf that regarded by the Fire Board officials as necessary for fire-fighting purposes and the engineer has recommended further cleaning to bring the less satisfactory localities up to the required standard/ * Reduction In Capacity After scraping and cleaning of the mains a coating of cement is forced inty) the pipes under pressure and this has given a smooth bore which not only accelerates the flow of water, but is calculated to give the old cast iron mains a further life of usefulness of 50 years or more. It was found that some of the older mains in the residential areas, which have been iu use for up to 55 years, were so encrusted |hat their capacity ivas reduced by about 50 per cent, but this'capacity has been almost wholly restored by the new treatment. The 'waterworks engineer has shown that for ordinary domestic purposes the pressure should not be below 401b. or above 801b. to the square inch, as-lower pressures give an unsatisfactory service and higher pressures are- apt to cause water-hammer and rapid leakage of washers.' A minimum flow of 200 gallons a minute is considered effective for fire-fighting in these areas, although a good deal more is necessary in commercial areas. Increasing Demand In the residential localities so far dealt with and tested the lowest pressure recorded was 501b. Prior to streatment the flow showed an average of 170 gallons a minute and the recent tests give an average of 278 gallons, which can be regarded as highly satisfactory. The increasing demand on the water supply is approaching the capacity of the chief distribution mains in the city, and Mr. Mead has recommended the replacement or reconditioning of a nunfber of sections at an estimated cost of £23,600 and tho scraping and relining of 44 miles of mains in Grey Lynn, Archhill, Newton and'"Eden Terrace, Grafton, "part of Epsom and part of Pefniiera, at a cost of £6OO a mile. The City Council has decided to make provision 'in the next loan proposal for the raising of £50,000 to carry out these works. >.