HAWERA’S WATER PRESSURE.

Hawera Star, Volume XLV, 16 June 1925, Page 9

HAWERA’S WATER PRESSURE.

AN ALTERNATIA r E PROPOSAL. SCRAPTNG THE PIPES. ENGINEER’S INTERESTINGREPORT. “If one cannot do what is best', it often happens that the only thing is to do the next best-, so-as to tide over until the* financial situation lightens, stated the borough engineer (Mr J. Sturrock) last evening in a written report to the Hawera Borough Council on a proposal to increase the flow of water through the main by scraping the pipes. _ ’ The report, which was referred to a meetino- ,of the general committee to be held shortly, gave the following information : “Our 10-ihch main has now been opened in many places for repairs and the condition of the internal surface of the pipe ■ observed. At no place has there been noticed a coating of incrustation covering the whole internal surface of the pipe. The original coating is. indeed, in as good condition as when laid, save for the presence of scatered nodules, distant from each other probably about four inches on an average. " The nodules vary in height and size, but might average roughly about half an inch in height. ‘‘lt mav seem .strange of realisation that these scattered nodules .should reduce tlie quantity of water carried by the pipe to any appreciable extent; yet such is the case. Eddies are formed ■n the water round the nodules and the fora ai d useful flow of water is tartly converted into little whirlpools which' expend their force, to. no. useful io.se. In this way the force of the water and its pressure are lessened. “Before I took up duty here a pipescraper, hatch-boxes and other waterworks fittings had been ordered out of loans. The cost of materials alone swallowed up the money and none was available for doing the work.

“In nearly all the pipe-scraping schemes which are reported upon there •s duplicate or triplicate supply to the population, so that, in the event of the scraper being lost in- the pipe during scraping -aerations, no water famine is axperienced. In our case- at Hawera 'oss of the .scraper in the main would entail serious consequences.

“Nearlb all the ; engineers whose reoorts I have reach agree that, after pipe-scraping, has been once performed,, nodules- grew more rapidly on*, account if the injury effected to the bitumin>us lining of the* pipe, and scraping requires to be regularly carried out thereafter. Such subsequent scraping, "owever; is much .more .rapid';* and' easily carried out since the obstacles ixperienced on the first occasion have been removed. These may consist of otruding lead, .pieces of roach metal, ate.

“Til mv urevious reports pipe-scrap-ing was not recommended-as a- cure- for oui* c trouhle. It is obviously, only- a temporary- measure, whereas what we require is additional pipe' room. Atthe time of’ first writing, the full effects of tlie present slump- were not. understood fully. At the present date a loan for duplication of the 1 main would admittedly, create a. burden greater than could he lightly imposed. “Short of being able to see the- inside of the pipe from-end to end, it is impossible to foretell with any accuracywhat relief mav be .afforded by- scraping operations. A’Cfe have therefore to fall back upon tests of the quantity, conveyed by the pipe. Some time ago the flow was tested, and found to be about 400 gallons per minute instead of- 500' gallons, which should be conveyed by a. pipe which is reasonably clean. This test' must not be thought to represent tlie quantity available at high or aver-age-pressure, for the test was made, as usual, at surface level to give definite data-for hydraulic calculations. “We might' expect, therefore, about 25 per cc-nt. extra water after scraping. The effect upon the pressure- should also lie appreciable, but, owing to. the constant variations, would be more difficult of statement. Once scraping Has been performed renewal, is required, and. at what period depends upon the nature of' the water. When we consider that, after 25 years’ service, our main has collected, nodules only, it is evident that the Rapuni water is not active ia nodule formation. I should guess that' the pipe would be the better of scraping every two or. three "rears thereafter. Such- repeats would be accomplished by our own staff. “I egnnot imagine tlie operation of scraping- the main extending beyondqsix month's i but that is admittedly only a guess, although it is a guess with a fit tie- judgment- behind it. “Accurate estimates of the cost are ‘ni possible. lacking the gift- of prophecy. There may- be few obstructions, or there may-’be many. I should' guess the sum: to be between £IOOO and £3OOO. That is all L can say,. There ire - no data: “The advisability of doing the work is &• matter for- the .council!s determination. If mv means of entirely prohibitiig the. use”*ofv the garden hose during certain months it is thought that our i troubles may be tided over for a sufficiently long period to enable the market to recover, then scraping may be thought' unnecessary; It all depends upon how long the slump may last and upon whether tlife people are prepared to' endure the lessening pressure. “Admittedly, however, our particular case gives one a problem which is iinilbasant, becaues of the trouble, which would ensue upon stoppage of a, pipe -which alone supplies a community.”