TOWN WATER

Southland Times, Issue 20447, 27 March 1928, Page 6

TOWN WATER

INADEQUATE SUPPLY ACTION BY CHAMBER OF COMMERCE RETICULATION SCHEME TO COST £24,000 In view of the attitude of the Underwriters’ Association of Otago and Southland, in forwarding a letter to the Chamber of Commerce warning them of the possibility of a rise in premiums owing to the inadequate water supply for fire fighting purposes in the city area, the business section of Invercargill is looking forward with keen interest to the report of the committee under the control of Mr. J. H. Reed, president of the Chamber of Commerce, which was set up last Thursday. It is understood that the reticulation scheme now in existence was laid for a much smaller town, and, with the growth of importance of the city area, a complete scheme will have to be drawn up to bring Invercargill to the standing of towns of equal size. Not only are the pipes not large enough to give the supply, but owing to the strong deposits of iron in the town water they are very much corroded, and no sense of safety can be felt among business people until cuch time as an up-to-date system has been installed. It is estimated that the cost would be within the vicinity of £24,000, but business men’s opinions are that the outlay would be more than compensated for in the added safety experienced. BRIGADE SUPERINTENDENT. The matter has been brought up before, as the appended reports show. Following is the report of Superintendent Simpson of the Invercargill Fire Brigade, which was submitted at the monthly meeting of the Fire board in December 1927, and forwarded to the Borough Council:— In considering any proposal for betterment, the arguments raised between the Borough Council and ourselves during the controversy over the steam stand-by plant cannot be overlooked inasmuch as pressure entered very largely into the discussions: It should be distinctly understood that pressure and velocity of flow are essentially to be considered together and ase necessary to keep a main of any size charged to its full capacity. Many lose sight of this fact, but as an instance I give you the following on very good authority:— With a water main of four-inch (4in.) diameter with the water flowing therein with a velocity of one foot j>er second it is possible to discharge 1961 gallons per hour but, increase the velocity to five feet per second and the discharge will be 9806 gallons per hour: If the velocity is further increased to seven feet per second the discharge will be increased to 13,730 gallons per hour.

Against this we will take an eight-inch (Bin.) main with the same velocities: Ist, one foot per second, discharge 7843 gallons per hour; five feet per second, discharge 39,210 gallons per hour, and seven feet per second, discharge 54,910 gallons per hour. This clearly shows that, under certain circumstances, in this case of increasing pressure, or velocity, or rate of flow, a fourinch main will discharge more than an eight-inch main in whictrthe velocity has not been increased, and as a further illustration the figures given above may be repeated. We will assume that with a "fourmeh main the rate of flow is increased from one to five feet per second, the discharge will be greater than from an eight-inch main with a velocity or flow of one foot per second, with a far more satisfactory discharge in favour of the four-inch, as far as fire-fighting is concerned.

Even supposing we were feeding our pump from stand-pipes affixed to an eightinch main with a low pressure, or rate of flow, the water in the immediate vicinity of the standpipes becomes exhausted, our canvas hose used as feed lengths collapse, with the result that our pump is restricted, whereas if the rate of flow, in other words, if the pressure, is increased, there would be ample supplies to work at full capacity. As an experiment in direct suction from the main, I, on Wednesday, conducted a series of tests in Esk street: In the first place I took readings for flow with normal pressure (tower pressure) as recorded on our gauge, direct from the main through a stand-pipe and one hundred feet of 2|in. canvas hose: The flow was too low to record so I then passed the supply through our No. 1 pump and recorded a flow of ninetyfive gallons per minute at approximately thirty lbs p.s.i. at which stage the canvas feed hose was on the point of collapse. Disconnecting the canvas feed we replaced same with our three-inch armoured suction hose and got a direct suction from the. main: The result was a flow of 175 g.p.m. with a pump pressure of 601bs p.s.i.: Replacing the flow gauge with a branch fitted with a one-inch nozzle, a pump pressure of 105 lbs was generated there by discharging approximately 215 gallons per minute. During these tests the pressure recorded at the Fire Station only fluctuated 51bs. Therefore with large mains with a low velocity we would not be a great deal better off than at present unless there were sumps into which the full bore of the main could be opened or unless there were some fittings on the main to which we could connect direct our five-inch armoured suction hose: In the latter case there is a possibility of doing the same as with our canvas hose, that is, causing a collapse of the main should we happen on one with a weakness. There is not the slightest doubt that something will have to be done: The samples of mains which have been lifted from time to time speak for themselves and demonstrate clearly that some of them will need replacement, certainly nothing less than six-inch should be laid, the larger the better from my point of view, especially in the business part of the city where it is often necessary to take two or more deliveries from the one main. Endeavours should be made to run all new mains under the footpaths, within the business area at least, so that stand-posts or underground hydrants, with two-way outlts, may be used. This is, I believe, the practice wherever permanent modern roads are being laid so as to avoid interfering with the surface in cases where a connection is to be made at any time. • It also does away with the trouble, met with at various times, of the covered fire plug. I trust that I have made myself clear that the question of pressure enters considerably into any undertaking affecting the improvement of our water supply: With a constant high pressure and the duplication or replacement of some of the older mains most of the difficulties which have caused concern for years past would practically disappear, not only in the business area but throughout the borough generally. INSPECTOR HUGO’S REPORT. Following is the report of the Inspector of Fire Brigades, Mr T. T. Hugo, in his report to the Fire Board last month:— “I would agayj call attention to the inadequate water supply for fire extinction purposes and which, as proved in part during my inspection, has now assumed a very dangerous aspect with every possibility of a disastrous fire occurring in consequence. “Unfortunately, through failure to obtain an interview with the Town Engineer, I was unable to procure certain information in regard to the present supply, but following upon my lengthy experience of the growth of New Zealand towns, and in view of the future possibilities of Invercargill in that respect I set out below what I consider should be the minimum size of distributing and reticulating mains in any new scheme for improving the water supply within the more risky business area, an area, say, bounded on the north by Leet street and on the south by Tweed street, on the east by Doon street and on the west by the water front. “In supposition that the supply carrying main from tower or gravitation source

comes in from the north or east, the distributing mains would have to be laid as follows: A twelve-inch pipe along Doon street from Tweed street to Leet street, thence down Leet street to Dee street and feeding two eight inch mains on the east side of Dee street. Another eight-inch main from the twelve-inch main in Doon street down Tweed street and connected up with the continuation of the eight inch main running along the west side of Dee street. All intermediate reticulation mains to be not less than six inches in diameter within the said area. The above recommendation is on the basis of a minimum pressure of 80 lbs.” An exhaustive study of the subject will be undertaken by the committee set up by the Chamber of Commerce, and their report will be presented at the next meeting. In the meantime Invercargill business people will be considering whether a better reticulation scheme is cheaper than increased insurance premiums.