WATER SUPPLY.

Poverty Bay Standard, Volume I, Issue 286, 15 November 1884, Page 2

WATER SUPPLY.

A few meetings back the clerk announced to the members of the Borough Council that he had received a report on the “ Holly Water Supply,” and as many of the items were thought to be applicable to local requirements it was deemed advisable to have the report published. We therefore present the document to our readers:— The Holly system of waterworks consists in pumping engines of a special and superior construction, which force the water intended for the domestic supply and fire protection of the town directly into the mains and distributing pipes, no reservoir or stand pipe being interposed. In order to maintain a steady pressure the operation of the machinery is continuous: but, as the demand for water is subject to constant variation, means are provided for the automatic regulation and government of the pumps, so that the amount of water delivered is in exact accordance with the requirements of the moment. Without such regulation, which is the essential feature of the Holly system, and which is fully covered by the patents of the Holly Company, direct pumping involves great waste of water. It is impossible to adjust an engine adapted to supply water always under uniform pressures to meet a fluctuating demand. Water consumption varies with the day of the week, and the hour, and actual experiment in Boston, Mass., has demonstrated that it is about four times greater between 9 and 10 a.m. that it is between midnight and 1 a.m. No provision, however, can adjust an ordinary engine to meet probable conditions of diminished demand, for the reason that unexpected drains are always liiiely to be made up by fires. A sufficient pressure must always be carried to meet not only the probable requirements, but a reasonable excess. That this involves the pumping of water which is not used is evident, and as the whole object of spending money for the

lion and maintenance of waterworks is to yump or supply water fox useful purposes, xt follows that every gallon not so appliec represents a certain amount of unnecessary wear of machinery, of strain on pipes and fittings, and a certain sum of money lost. The means of regulation which thus form* so important a feature in the Holly system is an exceedingly simple mechanical device, depending for its operation upon the degrei of pressure in the mains. If the pressure falls, owing to an unusual drain, the regulai to instantly acts so as to admit steam for a longer period into the cylinders of the engines and the pumps are thus at once caused t operate more rapidly and powerfully. When the pressure in the mains increases, owing tc the small draft being made upon them, tin reverse takes place, and less water is pumped The normal pressure is adjusted by the engineer, in accordance with average requirements. The fire protection afforded by th< Holly system is of the most efficient character. It is a fact not fully understood that the introduction of the Holly works dispensed wit) the necessity for fire engines. Water is not merely distributed to hydrants, but sent there under pressure, so all that is required is t< couple on the hose and turn on the stream An idea of the capabilities of the system maj be gathered from the following example At Rochester, New York, on the occasion of the official test, a 4in. horizontal stream—a solid column of water—was projected a distance of 465 ft., and thirty lin. streams at one time were thrown to a height of 135 ft. The adjustment of the engine to give a quick supply under heavy pressure, in response to a sudden alarm of fire, is the work of an instant. The mere opening of a hydrant causes sufficient diminution of the pressure in the pipes to operate a valve, which in turn communicates with a whistle, the sounding of which is the alarm for the engineer to turn on the fire presaure. To recapitulate, therefore, the essential features of the Holly system are 1. Direct pumping into the mains, and consequent saving of the heavy cost of distributing reservoir or stand-pipe. 2. Self-regulation to accommodate a fluctuating demand, thus saving fuel and wear and tear of machinery. 3. Prompt and efficient fire supply. Water delivered in powerful streams, to the extent of corporate limits, and the expense and maintenance of a fire department saved, besides large reductions in insurance rates effected.

To these advantages is to be added the fact that the Holly engines have given, not onlj under elaborate engineering tests, but undei conditions of actual experience, results which show them to be more economical in fuel and cost of maintenance than any other machines operating under conditions in anywise similar. To more fully illustrate the working of the Holly engine, let the following case be assumed —An engine of a capacity of 1,000,000 gallons per 24 hours is supplying a town containing 3,000 inhabitants, and delivering for domestic and corporate purposes 90,000 gallons per day, that is at the rate of 30 gallons per head. One-third of that quantity will probably require to be passed through the mains between 6 and 10 a.m., and the pressure requisite on level ground would not exceed 301bs to the inch. The engine will have to pump against the pressure from 6 a.m. to 10 a.m. at the rate of 125 gallons per minute, and from 10 a.m. till 6 a.m. at the rate of 50 gallons onlj per minute. The fuel consumed would be in proportion to the work done, and yet there would be in reserve and ready to operate at a moment’s notice, a capacity for delivering for fire purposes 694 gallons per minute at a pressure of 521bs to the inch. Scheme for Blenheim. The site of this town is exceptionally favorable for the introduction of the Holly system, there being an unlimited supply of portable water of first quality obtainable which will rise to a sufficient height to fill the mains without pressure from the pumps. I should recommend the adoption of a 26 h.p. quadruplex engine, having a capacity of 1,000,000 gallons in 24 hours, against a head of 12vft; this would throw four lin. diam. jets about 90ft high, discharging 680 gals, per minute, or this would be equivalent to a column ol water 2in. in diameter, 90ft high—a body of water sufficient to drown out any ordinary fire in a few minutes.

The water would be forced by the engine in mains reticulating the town. These mains would form the chief item of cost in devising a complete reticulation for the whole of thtown, in consequence of the large area, viz.. 1571 acres, comprised within the boundaries of the Borough. I consider it would requirt 7j miles of mains to protect the chief part oi the town, and this could only be done bj reticulating the outer streets alternately, arranging the mains in such a manner so a; to bring the hydrants within 5 chains oi every building of the part of the town reticulated, To reticulate the whole of tht inhabited parts of the borough would requirt about 15 miles of mains: but as the water h required chiefly for fire protection, and as the 7J miles before mentioned would reticulate all the streets in the business part of the town, besides affording efficient protection in all those parts of the borough most built upon, I have estimated the cost of a scheme upon that basis. Estimate. Pumps, engines, and wells complete £4,500 71 miles of mains, including hydrants and sluices .. .. 6,243 Contingencies, including land purchase .. 1,074 Engineering, legal, and financing.. I,OOG £12,817 Say including 100 house services .. £13,000 For the more complete scheme comprising the above items, and in addition 6| miles more of mains, making a total of 14 miles, the cost would be as follows: — All the items as before .. .. £13,000 6| miles of mains complete .. .. 5,000 £lB,OOO I will now give an approximate estimate for a gravitation scheme based upon the data previously given to the Council by Mr Dobson. It was proposed in that scheme to bring water from the Taylor by a force main Bin. diameter and 8f miles long, the intake being placed 400 feet above the town. This pipe would deliver barely enough water to supply two lin. jets 100 ft. high, being about half the capacity of the Holly scheme just described, whilst the prime cost would be nearly twice as much, and the annual cost 25 per cent, more than the Holly system, as the following approximate estimate will show : — Gravitation. 14 miles of mains as previously esmated for the extended Holly scheme .. .. .. ..£11,306 8J miles of force main Sin. deal .. 12,150 Dam .. -.- • • • • • 2,000 Storage reservoir 4,000 £20,456 Contingencies 10 per cent .. .. 2,945 Surveys, land, engineering, legal, and financial expenses, say .. .. 3,000 £35,401 Thus we have the prime cost as follows:— Holly, £lB,OOO Gravitation £35,401 The annual expenses would be as follows: — Holly £lB,OOO at 6 per cent. .. £l,OBO Operating .. .. - • • • 600 Total £1,680 Gravitation £35'401 at 6 per cent... £2,024 To recapitulate: Gravitation would cost twice as much for half the service, and cost annually 25 per cent, more, and if sinking fund and life of the force main be taken into account, the comparison is still more in favei of the Holly system. I will now upon the basis of the Holly system, with 7| miles of mains, estimate the probable cost and income derivable. Estimated cost as per details already given .. .. £13.00C Interest at 6 per cent. .. •• Cost of operating .. .. .. 60C Total £14,38( Per Contra— Sale of water for domestic purposes £250 Water for machinery .. 100 Gardens, stables, Ac. .. 30 £3B( £100(

Leaving £lOOO to be prowided for out of the ;ates, which would be rather less than a hilling in £ if levied over the whole of the lorough, and probably about Is 3d if applied mly to the central part of the town proposed :o be reticulated by the 7| miles of mains. In this estimate it is assumed that the )umps are run by steam power, but as there s a good deal of water power in the neighborhood of the town, it is quite possible that on nvestigation it may be found practicable to A-ork the pumps by water power, in which ise the annual cost would be greatly lowered, nd the prime cost also, unless the power was •btainable at such a distance as would entail i heavy cost for the connecting main. The jrice required for the purchase of the rights would also form an important element. As an illustration of the low cost of work, ng when using water power, at Mortinsbury, W, Ya., with 6000 inhabitants, the yearly cost for running is quoted at $lOOO, £221 ss.