Sewers: Storm Versus Sanitary

We’ve come a long way from the days when human waste was not treated. Early sewage systems just flushed it away, with water and rainwater “combined” to help it along. Dilution was the solution. And back then, horses were the main mode of transportation—what happened to that waste? Much waste from all sources ended up in streams and rivers, which flowed into lakes and other bodies of water.

This all started changing around 1870, when people realized the connection between disease and human waste. Because rivers and lakes often were the source of drinking water, cities searched for solutions. Major cities started using sewage treatment methods around the year 1920 and treated water became the norm. Think about it: No treatment methods could have worked before then since there was no widespread use of electricity or motors or pumps until about 1920—so how could there be sewage or drinking water treatment?

New ways to handle rainwater 
Today, we have modern systems that separate human waste from rainwater (Illustration P017C). The storm sewer carries away rainwater (sometimes called storm water) through a series of pipes in the street and discharges this water to rivers or lakes. The catch basin in a city street collects rainwater for the storm system. In rural areas, roadside ditches handle rainwater. 

Older cities may have a “combined” system in which sanitary sewers and untreated waste flow together, but often this overloads the treatment plants during a heavy rain (Illustration P165C). Many cities are separating these sewers or building deep tunnels to capture sewage and treat it later.

The sanitary sewer system in a city routes human waste to a sewage treatment plant. Rural areas often require private septic systems—that is, a septic system for each home (Illustration P121C). Septic tanks should be pumped to remove settled sludge and scum (oils and soaps) at least every other year. There also may be a screen that needs periodic cleaning. In this case, you should advise clients to secure the maintenance records and arrange for a specialized inspection of the septic system.

What must you look for? 
You must understand the basic sewer systems used in your area and be able to recognize components that could be installed improperly.

In a home with a septic system, you will often find a sewage ejector crock and pump. This lifts sewage into the discharge pipe midway up the basement wall. In some cases, this may be a “gray water” crock that pumps water from the floor drain and the laundry tub. 

Watch for a sump pump that may be dumping clean water into the city sanitary sewer; this presents a problem (Illustration B092). Also, watch for a sewage ejector that may be dumping gray or sewage water to grade; this workaround may have been installed to cover up a failing septic system.