As America's cities began to grow and their population densities increased (and the continued use of privies and cesspools became more problematic), two potential approaches were possible: those with storm sewers could make them "combined" sewers (combining storm water and sewage), or they had to create "separate" systems for dealing with sanitary sewage. Most likely, the first scenario was the choice for cities with the "wrong" combination of heavy precipitation (rain and snow) and relatively flat terrain. Cities with rolling/steep terrain (i.e., good storm water runoff and/or spare precipitation) generally faced the second situation. [Sometimes, cities also considered doing a new combined system to deal with both types of wastewater -- especially if they believed that their towns/cities would continue to grow and "harden" (i.e., have more concrete, buildings, hard surfaces, etc.).]

The principle of creating separate systems for receiving and conveying human wastes was developed as early as 1842 in England by Edwin Chadwick (considered by many to be the "Father of Sanitation" in England). Other English engineers, such as Sir Robert Rawlinson, carried the same philosophy forward in later years.

The concept of separate systems received much review by American engineers; they had a quiet respect for their English peers. However, the natural difference between the character of the rainfall in Great Britain and that in the United States had a significant impact on the best choice of the type of sewerage conveyance system that should be built for each town. The English rains were less intense but more frequent -- thus, the greater need for flushing of their separate systems. America's storms (in general -- especially in the areas easterly of the Mississippi River) were less frequent but more intense; hence, the larger diameter combined sewers could work somewhat better since they'd get a good flushing naturally once in a while. Neither of the general situations noted above made it particularly easy for a city/town to choose one or the other; it really depended on local conditions, climate, history, and fiscal ability. Some American lessons in the application of separate systems were about to be learned in Memphis, Tennessee, in the late 1870s/early 1880s.

Memphis suffered through several severe plagues of cholera (1873) and yellow fever (1878 and 1879) -- over 10,000 lives were lost. The city recognized the need to get their sanitary sewage away from their water sources (then, primarily small private wells), even though the final decision was erroneously based on the belief that yellow fever was being caused by inadequate sanitation practices. The city and the state legislature tried to raise monies; the efforts gained some of the money they thought would be needed for a new sewer system -- but not a lot.

The situation in Memphis aroused the sympathy of the nation and was largely responsible for the creation of the National Board of Health. The Board retained and sent Col. George E. Waring, Jr., to Memphis. He designed what he thought was a system Memphis could afford, but also one he felt would work: a separate system using 6" diameter laterals, with sewers with 112-gallon flush-tank mechanisms placed at the upstream terminal end of each of the lateral (collector) sewer runs -- to be flushed once every 24 hours. The house connection sewers were 4" diameter. Both vertical and horizontal changes of alignment were routinely done along the long runs of manhole-less gravity sewer mains. No more than 300 homes were to be connected to each 6" main. No rain water was to be made tributary to these sewers and the sewer system was to be vented through the soil pipe plumbing system in each house. NO (!) manholes were included; only lamp-holes were provided. (These lamp-holes were soon recognized as failures: they provided little or no maintenance access, and their vertical weight often crushed the main line sewer.) Soon, the number of blockages in the manhole-less sewers (and the difficulty realized in removing those blockages without having good maintenance access) convinced the city fathers that Waring's original approach was somewhat flawed and in need of alterations. Soon the "Rawlinson" approach -- the use of manholes, placing manholes at all changes in horizontal or vertical alignment, and the use of larger (no less than 8" diameter) gravity sewer pipe -- was deemed to be a better idea, one that should be blended in with Waring's basic approach. Waring agreed to the changes, and his designs were used to expand Memphis' system, and as the basis for separate systems in many other communities (Lennox, MA; Norfold, NI; Omaha, NE; San Diego, CA; Buffalo, NY; Tucson, AZ; and Dayton, OH) during the 1870s-1890s.

The city of Memphis, TN, is considered to be the first community in the United States to have a separate sanitary sewage collection system. About this same time, the City of Pullman, Illinois, also built a separate system -- designed by B. Williams and approved by E.S. Chesbrough.

The National Board of Health was alarmed by the results of the first application of Waring's ideas in Memphis -- to the point that they sent Dr. Rudolph Hering to Europe in 1880-81 to tour/review European systems. His ultimate report (the "1885 Report") reached some conclusions relative to separate systems, more specifically, that they are suitable for use when:

• An area's storm water runoff (quantity, frequency, etc.) does not require underground storm sewers -- instead it can be handled by surface ditches, drainageways, etc., or simply via "over-the-top-of-the-ground" approaches.
• There's an existing storm water sewer system that is sufficient in size for the runoff water, but not of sufficient size/design to also accommodate the area's sanitary sewage. Then a new separate system for sanitary sewage (human waste) is applicable.
• The pumping of the sewage is required -- especially when both the storm water and sanitary sewage would have to be pumped if they were to be conveyed to the pump station in the same (combined) sewage conveyance system.
• The homes' wastes systems needed quick relief, and monies were not then available to build a larger combined system.

To the contrary, Mr. Hering believed that a combined system is the preferred choice for use:

• Where rain water must be carried underground from extensive districts, especially where closely built up and where new sewers must be built for this purpose.
• Where purification of sewage is not required or is not difficult, and where storm water overflows are not objectionable in polluting the streams.
• Where a sufficient amount of water or sewage is available for flushing the larger sewers -- i.e., where there's a lot of existing sewage and/or the area in question receives a relatively high level of annual precipitation.

Thus, each community was left to choose the type of sewerage system that was best suited to its area's needs and its financial wherewithal. A lot of both types of systems were designed and built in the succeeding years.

As noted earlier, the homes/businesses in many American towns were initially served by privies; storm drainage was mostly accommodated by surface runoff (except in flatter terrain areas where larger storm sewers were employed).

Europe's older cities' sewers started off more as storm sewers -- with human sewage being added over time (when contents of chamber pots were flushed off the streets by rain into the sewers, or when night soil was deposited directly into the sewers, or by direct connection of the homes to the sewers). Since storm water was the primary reason for the sewers, they were large to begin with.

The growth of metropolitan areas in the United States began to explode, starting in the 1840s; it continued to do so on through the turn of the century. More people were moving into these areas. Water systems (initially, wood log pipes, then cast iron) were being implemented by cities and towns for two basic reasons: 1) for fire fighting, and 2) to deliver water directly to individual homes and businesses. Per capita water usage changed dramatically: from 5-15 gal/day (before the presence of municipal water systems), to volumes ranging from 75 gal/capita/day up to over 150 gal/capita/day! Once the water was easily/readily made available, the use of water closets (a device whose creation dated back centuries, but was only patented in England in the late 18th century, and in the United States in 1833) soon came into prominence. Before water closets came into use, the "necessary" or "privy" (both Victorian euphemisms) in the backyard was the facility most often utilized.

With the advent of the ability to have sufficient quantities of water delivered into the home, the use of the water closet slowly evolved. When they were a new phenomenon, water closets were installed in the middle of homes (mostly, by the well-to-do), but the early devices did not have seals/traps adequate to keep odors from the receiving vaults and cesspools from coming back into the living areas. Soon people began installing them at the rear of the house -- often near a chimney (so that the foul odors could instead be vented up and out through the chimney). Soon better seals (and other devices such as those provided by a company named "Jenning's Sanitary Specialities") were developed for the water closets and/or the involved waste piping systems.

In most cases in the early days, since sewers were not available, wastes from the new water closets -- and kitchen drains -- continued to go through soil piping to the vaults and cesspools beneath the old privies. Their use overloaded the privy vaults/cesspools.

Some municipalities implemented the philosophy that when a vault or cesspool for a home/building was no longer functional, abandon it, cover it over, and build a new one nearby. Others tried to implement a community program to periodically clean out the vaults. However, this approach, which was accomplished (mostly at night) by either city employees or private contractors, was found to be quite expensive and annoying (odors). The involved poorly sealed carts that hauled the wastes away (often for use as fertilizer on farms) often left an undesirable trail behind them.

The overloaded and often overflowing privies/cesspools were quite frequently located near sources of drinking water. The connection between diseases and contaminated groundwater was beginning to be recognized (although not yet fully understood).