The principles of waterworks engineering

Front matter

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Preface

The art of the Civil Engineer consists, to use the language of Thomas Tredgold, of the " practical application of the most important principles of natural philosophy."

Whilst examples of sound engineering practice are within reach of all, the laws that govern it are frequently obscure. An orderly statement of the facts ascertained by experience, will, however, throw light upon the principles involved. It has been our aim to investigate and classify the observations and rules employed, and to trace the steps taken by the engineer in proceeding from the inception to the completion of schemes of water-supply.

From the data afforded by experience of executed works, and of the properties of materials, designs appropriate to the requirements of varied circumstances may be elaborated ; but the fixed laws of natural philosophy must not be ignored by the designer, in applying the conclusions derived from his observation of facts and phenomena.

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These considerations have led us to neglect the historical aspect of the subject ; because during many ages, limited mechanical and metallurgical knowledge and an imperfect acquaintance with the laws of hydraulics, prevented the ancients from leaving to us many examples of waterworks which can be prudently copied. It is only by scientific investigation of the circumstances of individual cases, that false analogies are avoided between more recent practice and the requirements of works contemplated. ** The site of a spring or the presence of a stream," says Professor Prestwich, " determined probably the first settlements of savage man ; and his civilised descendants have continued until the last few years equally dependent upon like conditions." The resources of nature are by the skill of the engineer now rendered more accessible to mankind ; and communities are enabled to obtain water without regard to the depth and remoteness of its source.

In the following pages some knowledge of physical laws is assumed, and we endeavour by their aid to set forth the principles of the design of waterworks —-illustrating these by examples of recent practice. A comprehensive grasp of the subject will be best afforded by the consideration of its separate elements. Each one of the eight chapters in which we seek to develope an outline of this branch of engineering, comprises a statement of matters which, if not

PREFACE. IX

necessarily related to one another, are conveniently grouped together — the several articles being rendered as far as possible independent, but referenced one to another where their subjects naturally touch.

The first chapter treats of the '* sources of water-supply," and of the preliminary considerations involved in the selection of such sources. In the second chapter the " measurement " of water is introduced, forming the foundation of what may be termed the science of waterworks engineering. ** Collection," in the third chapter, treats of the methods employed in obtaining access to sources of supply, with an account of the appliances used to abstract water therefrom. The fourth, fifth and sixth chapters comprise respectively the '* storage,*' *' purification," and *' conveyance '* of water — the last subject embracing the design, construction and use of aqueducts of various kinds. The important questions concerning the '' distribution " of water, occupy the seventh chapter ; and the book is concluded by a brief statement of some important considerations that affect the '* maintenance of waterworks."

For many of the mathematical methods and expressions employed, we gratefully acknowledge our debt to previous writers. Many are original and appear here for the first time. In particular, the subject of masonry dams is treated by a new method — the object of which is to determine by easy

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calculations an economical dam-section that rigidly conforms to the primary conditions of strength and stability laid down at the outset of the investigation. The extent to which mathematical treatment is desirable in a work of this character must be largely a matter of opinion ; but there can be little doubt about its utility in often presenting more concise and explicit statements than are afforded by verbal expression. To this extent we have employed it — endeavouring to take advantage of its aid, but not to magnify its importance.

We have not sought to describe operations that are common to every kind of engineering construction ; and in occasionally adverting to details that are peculiar to this class of undertakings, we would disclaim any attempt to teach arts that can only be acquired by contact with the work itself.

Our object has been to provide, for the use of those engaged in the construction of waterworks, an orderly and logical statement of the matters that specially occupy the attention of the engineer ; presenting the subject in such a form as to be both serviceable to students, and instructive to that large class of persons who desire some general but accurate knowledge of a subject to which their attention is compelled by the sanitary progress of this age. In alluding to executed works, elaborate descriptions have been avoided ; their proper place being, in our

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opinion, in the pages of the scientific and professional journals, where, for the most part, they originally appear.

Every acknowledgment is tendered for the great assistance we have obtained from the numerous publications referred to in the text — particularly those of the Institution of Civil Engineers. The wide range covered by the practice of the hydraulic engineer, and a desire to state within a reasonable compass the principles that guide him, may, we trust, afford an apology for such want of elaboration and detail as the reader may feel in the perusal of these pages.

J. H. T. T.

A. W. B.

London : June^ 1893.

/^ ^ OF THE * \

fUNlVEBSiTT/

Chapter I. The Sources Of Water-supply

PAGB

Properties of water — ^Absorption of impurities — Chemical and biological examination — Modes of the natural occurrence of water — Its aerial and subterranean courses — Rain, surface-water, streams, springs and wells — Elementary considerations as to quality of water and feasibility of procuring it — Use of the barometer in preliminary surveys — Compensation for interference with streams i

Chapter II. The Measurement Of Water

Hygrometry — Eain-gauging — Evaporation, percolation and absorption — Estimation of available rainfall — Annual, monthly and daily variations of rainfall — Flow of water in channels and pipes — Investigation of formulae--Gauging by notches and by orifices — River-gauging — Instruments and apparatus — General formulae — Irrigation modules — ^Water-meters .. 34

Chapter III. The Collection Of Water

Interception of rain — Surface-water, lakes and rivers — Intake-works— Catch-water drains — Filter-galleries — Shallow wells — Springs — Artesian and other wells— Well-sinking and boring — Pumps and other water-raising machines — Air-vessels and stand-pipes — Motive power — Types of steam-engines — Testing steam-engines no

XIV CONTENTS.

Chapter IV. The Storage Of Water

PAGB

Capacity of reservoirs — Selection of sites — Earthen embankments— Puddle-walls— Outlet-works— Waste-weirs — Stability of masonry dams — Design of profiles — Arched dams — Recent examples — Service-reservoirs— Tanks and cisterns .. 172

Chapter V. The Purification Of Water

Objects of purification — Settling-ponds — Natural filtration —

Filtration through sand — Design and working of filters—

Sand-washing — Purification by iron and by aeration — Softening water — Filter-pressing .. .. .. .. 262

CHAPTER VL

THE CONVEYANCE OF WATER.

Design of conduits — Delivery of conduits — Design and manufacture of pipes — Pipe-laying and jointing — Special pipes, valves and other appurtenances — Balancing-tanks — Relievingreservoirs — Railway- and river-crossings .. .. 317

CHAPTER Vn.

THE DISTRIBUTION OF WATER.

Variation of consumption — Proportioning mains — Zones of pressure — Reducing-valve— Connection with pipes under pressure — Stop-cocks, hydrants and other accessories — House-service — Systems of supply : constant and intermittent ; by measure and by rate ; duplicate system .. 382

CONTENTS, XV

CHAPTER VIII.

THE MAINTENANCE OF WATERWORKS.

PACB

Machinery and metal-work — Reservoirs and tanks — Pipe-scraping — Prevention of waste — Consumption of water in Great Britain and in the United States — ^Waterworks regulations 402

INDEX 421

^^^^Cr^LlFORNlA.

THE PRINCIPLES or

Waterworks Engineering