:
8
but an actual fact ascertained by the D. P. W., who informs me that he has personally observed it when the city has been under the intermittent system of supply;
and the water has been suddenly turned on at night for the purposes of fire extinction. I may add that I have observed the same thing not once but often, when I was examining the town in 1882 and 1883.
34. As regards (6). During the time that the water is turned off, it is a generally ascertained fact that the growth of fungoids, and the corrosion of the pipes are much facilitated, thus reducing their capacity for the conveyance of water and their probable length of life. Any one who had seen the condition of the old pipes on their removal, when the new mains were laid, would have no doubt on the point. They were often half full of black stinking mud. Truly, the water was not filtered in those days, but the deposit was not pure sand or clay, but largely composed of putrescent organic matter.
35. As regards (c). The continual shutting and opening of valves renders the pipes liable to severe shocks, and unless great care is excrcised may be the means of doing serious damage, sometimes depriving whole districts of water, during the repair of a burst pipe or displaced joint. The wear and tear of the sluice-valves is greatly increased.
36. As regards (d). Great difficulty is experienced in the equitable distri- bution of water, especially in the higher levels during the prevalence of the intermittent system. Taps are left open for the purpose of obtaining water as soon as possible after it is turned on. Now with a number of open taps in the lower portions of the district, the water is for some time drawn off through these taps as fast as it flows into the main, and consequently takes a long time to fill it, and the water may not indeed ever reach the taps at the higher levels of the districts. Also, the effective supply of the higher levels of the city and hill district is, to a great extent, dependent upon the working of hydraulic motors, which, again, depend on the constant and regular flow of water into the maius supplying the lower levels of the city.
37. As regards (e). Nothing encourages the proper closing of taps, the proper use of water, and the abolition of the insanitary storing of water in unsuitable receptacles, sometimes inside over-crowded dwellings-than the fact that householders know at all times they have only to turn on a tap to obtain water when required. When an intermittent supply is being given, all available vessels are used to collect the water, often far more is received than is required for the day's supply. The excess is thrown away on the supply being turned on. Again very frequently a vessel is placed under the tap utterly inadequate to contain the water which flows during the time of supply. No one takes the trouble to shut the tap, because it will cease flowing soon. Consequently the vessel overflows, and much water is wasted. I have observed this myself frequently in former times. The quantity of water that a tap discharges is scarcely appreciated. I believe that a discharge of 4 gallons per minute, or 240 gallons per hour, is a low estimate of the delivery of a tap in Hong Kong. In three hours a tap will therefore deliver 720 gallons, sufficient, at 10 gallons
9
per head, for 72 people. Left running continuously for 24 hours, about 500 taps would discharge the whole daily supply of about three millions of gallons.
38. As regards (/). The efficient extinction of a fire depends, almost entirely, on having water always available, and applying it at the earliest possible stage of a conflagration. Now, with the intermittent system, the exact locality of a fire must be ascertained before the water is turned on, valves closed to concentrate the supply to the district in which the fire is situated. The water must be allowed to fill the pipes gradually, so as to avoid excessive shocks in the mains. An appreciable time must elapse before sufficient pressure is obtained in the mains, especially when householders leave their taps open, to cope efficiently with a conflagration, which by the time that a jet can be brought to bear, may have attained considerable proportions.
39. Having thus pointed out the very serious objections that exist to the introduction of an intermittent supply, and from which, I think it is clear, that in the event of it being absolutely necessary to adopt such a system for any part of the year, the period during which such system is adopted should be the shortest possible,—I will now consider what the probable gain or saving of water would be, supposing such a system were adopted during the dry season.
40. It is clearly no use adopting such a system as long as the reservoirs are overflowing, and the filter-beds and distributing mains are equal to the effective filtration and distribution, of the maximum requirements of the population. I therefore propose to consider the saving of water, supposing that the intermittent system were adopted, from the 1st of October to the 1st of May, and that during that time the water were shut off, except in the case of fire, from 9 p.m. to 5 a.m.,, that is for eight hours daily for 212 days. According to the experience of 1893 the saving would amount to 420,000 gallons a day (cide table, paragraph 14), or, during the 212 days, to 89 millions of
89,000,000 gallons, or to
36 days' supply, at the reduced rate of consumption. 2,460,000 To attain this end the public must undergo for seven months the inconvenience of an intermittent supply, with its attendant danger to health, and increased risk of destruction of property by fire.
41. It seems, therefore, clear that intermission should be postponed to the last moment, and if it has to be adopted, then the water should be shut off for at least 15 hours per day. Indeed, it is worthy of consideration whether, if restriction has to be adopted, the best plan would not be to shut off all house services, leaving the people to obtain their water from public taps, temporarily erected, if necessary, in the manner adopted in England during frosts.
ESTIMATE OF MINIMUM SUPPLY.
42. Since the works have been completed there has not been any year in which the total rainfall has been much below the average. The reports of the Director of Public Works give the stock in hand month by month in the Tytam reservoir, the quantity of water discharged month by month, and the
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