I came across this article while going through old files, and thought it presented a clear and understandable overview of the city’s complicated drinking water treatment and distribution system. The comments about pollution of the source water no longer stand—the Delaware and Schuylkill rivers are no longer grossly polluted by raw sewage and industrial wastes—but the problems posed by the city’s large area and range of elevations are still valid today. I’ve been researching the city’s water and drainage systems for more than 25 years, and whenever I think I know it all I come across an article like this, which managed to teach even this grizzled water rat a thing or two he didn’t know.
One note about Hayes’s invitation at the end of this story: It was a different world in 1933; unfortunately, because of modern security concerns, the public today is not allowed to simply stroll into a plant and start asking questions. But occasional open houses are held, which you can learn about by visiting the PWD website.—Adam Levine
The story appeared in the September 1933 edition of The Nor’easter, a newsletter published by the Northeast Philadelphia Chamber of Commerce. It was included in a binder of documents, PWD Catalog No. 2009.002. A full issue of The Nor’easter from August 1939, with more coverage of the city’s water problems, can be viewed here.
PHILADELPHIA’S WATER
by C. THOMAS HAYES
Chief of the Bureau of Water
Department of Public Works
Philadelphia
Philadelphia has perhaps the most complicated water problem of any of the major American cities, all factors considered. In treatment of water, in pumping, in distribution, it must solve unusual difficulties. It has wide differences of elevation, hills and hollows, two different sources of water supply, both of which are very badly polluted, and it conducts the largest municipal filtration undertaking in the world.
What water treatment means to the people of Philadelphia appears in the reduction of deaths from typhoid. In the year 1907, with no filtration, typhoid caused 61 deaths per 100,000 population; in 1908, The Torresdale Pumping Station with perhaps half the supply filtered, typhoid dropped to 35 deaths per 100,000 population, and as filtration and chemical treatment became the practice for the entire water supply, the rate dropped still further. Advance in practice has continuously affected the reduction, so that the total number of deaths from typhoid for 1932 was only 13, making the rate less than 0.8 per 100,000 population.
The plant which stands today on the books of the Water Bureau, at a valuation of about $84,000,000, is not a thing of uniform and steady growth. It developed at first from the center out, and later from the outside in. A whole volume might be written on the various district waterworks—which the extension of the city’s boundaries from the original 2¼ square miles allotted by William Penn to take in the entire 129.6 square miles of Philadelphia county—brought under the City system in 1854. All this complicated its extensions and operations, in the effort to make the best possible use of old local facilities as parts of the new city wide system, into which local systems were absorbed. The effectiveness of the system was clearly demonstrated during the drought periods of 1930 and 1932, when nearly all other municipalities were forced to ration their water supply.
Engineers Met Many Difficulties
The troubles involved in coordinating these local systems nobody but a water engineer can realize. One easily understood was that of turning into local systems, built to stand very low pressures, city water under pressure three to four times as great. Another less simple to see was the reversal of flow of water in city pipes, when the supply began to be pumped from outside points toward the center of the city, instead of being pumped from the center to the city limits.
It is usual practice to lay water mains with the maximum size nearest the pumps, and taper off with smaller sizes the farther the water travels from the pumps, in order to keep up pressure as the quantity flowing is diminished by use. But when water began to come in from outer points, the nearest point of entrance was at the outer and smaller end of such city pipe lines, and it is some trick to pump enough through a small pipe to fill a larger one. But these are only minor problems. The 2500 miles of underground mains and the 12 pumping stations and five filtration plants are widely scattered, and not of a scenic nature to attract public attention. Yet every day an average of 340 million gallons of water passes into the intake.
Some cities have a long narrow or a square or rectangular area to serve with water, but Philadelphia is not only of great area, but of irregular shape and elevation. From the intake at Torresdale to the corner of Broad and Snyder Avenue is fourteen miles. From Torresdale filters to City Line and Cobb’s Creek is twenty. The Upper Roxborough filters are about seventeen miles from Torresdale and the level of the water in the filters in operation is 415 feet above the level of the Delaware River at the Torresdale intake.
Elevation Affects Pumping Work
This great variation of elevation makes pumping problems for the Bureau of Water. The pressure that leaves a man over on the high ground in West Philadelphia unable to draw water in the third story of his house gives South Philadelphia enough to spare. The family up in Chestnut Hill must go dry unless its water supply is given more pressure than the water that is pushed through the pipes to Tioga or Logan. The house on a hill at Somerton is in the same situation as that on the heights of West Philadelphia or Chestnut Hill. So the same pressure cannot be used for all parts of the city. Should that be attempted, there would be great pressure at the tap in low districts, and a trickle or perhaps nothing at all at the tap on a hilltop.
Therefore, it becomes necessary to install special pumps known as boosters, to keep low-lying districts from robbing the hill dwellers of their water rights. This sort of thing adds to the number of changes in the flow of water in the mains, and that brings fresh worries to the Bureau of Water. In all large water systems there are some changes in flow. If a cross street main hooks into a big main at each end of the street, for instance, it may draw sometimes from one big main, sometimes from the other, and sometimes from both. This works out very nicely. It is only when water has acquired a habit of flowing in the same direction for a long period and then suddenly reverses, that trouble comes. And it usually comes in the shape of complaints of what may be described as “red water,” which the Bureau of Water may be forgiven for describing as a Monday washday specialty in the complaint line.
The cause is very simple. Inside any water pipe rust is deposited. If you examine it carefully, especially with a microscope, you will see that the rust deposit resembles an army of little tongues all bent in one direction, that in which the water has been flowing during their growth. Any sudden reversal of flow of water catches under these little bent tongues of rust, breaks them away, and sends them floating along to the nearest tap that is opened, perhaps inopportunely into somebody’s laundry tub.
The 9,706 square miles of watershed of the Schuylkill and the Delaware, from which Philadelphia draws its water, receives a varying rainfall which at Philadelphia averages a trifle more than forty inches a year. The water of the Schuylkill is moderately hard and that of the Delaware moderately soft. Philadelphia’s problem is not only one of pumping, filtering and purifying more than 340,000,000 gallons a day from these two rivers, but it must also deal with the contamination which comes down from the population and the industries of two watersheds, which although each reaches into mountainous, rugged, wooded country, carry a large population, and must dispose of the waste of numerous and varied industries. The population has increased since the 1920 figures which gave the Delaware watershed 111 and that of the Schuylkill 265 per square mile, so that it is probably not far wrong to estimate that the waste of various kinds from 1,500,000 people, or a city of three-fourths the size of Philadelphia, must be reckoned as factors in the condition of the raw water which the Water Bureau takes from the two rivers for the use of Philadelphia.
Both rivers carry sewage. Both carry industrial waste, in dissolved and in solid form. The Schuylkill carries noticeably more trade waste than the Delaware. It is perfectly plain truth that Philadelphia’s raw water, as it comes into the intakes on the Schuylkill and on the Delaware, is wholly and totally unfit for the human stomach, and nothing but skillful and careful filtration, and chlorination stand between the 2,000,000 people of Philadelphia and an incursion of typhoid.
Existing conditions call for insistence on scientific treatment, and the utmost care in operating filters. They call for power and pumping adequate to any emergency, which means reserves over and above any contingency.
The responsibility of purification devolves upon the Water Bureau. The State Department of Health maintains an office here and a District Engineer of the Sanitary Water Board is at all times on duty, weekly reports of the bacteriological examinations of Philadelphia water being regularly forwarded to the State.
For the control work of checking up on quality of water, the Bureau of Water maintains a laboratory at the Belmont Filters, in which about 300 bottles of water are examined seven days a week, for B. C. index; parallel chemical tests are made five and one-half days a week, and weekly samples from the rivers direct are tested.
The great Torresdale Filter Plant with its sixty-five filter beds, each approximately three quarters of an acre in area, is the largest slow sand filter plant in the world. The pumping station, which pumps the water from the river to the filter beds, is completely electrified, and with its six (6) fifty million-gallon-a-day pumps, and its four filter washing pumps, its tiled floor and its brass railings, is operated with an almost unbelievably small force. The park around this station, with its fine lawns and shrubbery, is a very popular resort during the summer, and many visitors who are attracted by the inviting coolness of the park, have visited and inspected the pumping station.
Any citizen who wants to get an idea of what the handling of water means, is privileged to visit any of the filter plants or pumping stations, and standing orders have been issued that every visitor is to be shown every detail and each process and machine explained by experts.
