Flood control

In the Chicagoland area, and in Chicago especially, there are some pockets of problem sewers – areas where the city sewer is prone to be overwhelmed by heavy rains and back up into basements.  Of course this can cause a lot of damage, and it’s a health hazard as well.

Most cities in Chicagoland have done a lot of work over the last several decades to reduce the problem, but it still happens.

The origin of the problem really lies in the fact that many of the older cities and suburbs have combined storm and sanitary sewers, so all of the rain water is collected in the same pipe as the poop water.  Newer cities separate these two drain systems.

There are several different ways to attack this sewer backup problem, and one way is to install a flood control system in the front yard (or the yard leading to whichever way the sewer runs).  Here are the basic components of such a system.

There’s a large pit dug into the ground and lined with concrete, or sometimes it’s made from concrete blocks.  At the bottom of the pit runs the sewer line from the house out to the city sewer in the street.  And placed into this sewer line is a backflow valve.  The basic arrangement is that this backflow valve has a flap that can only open in one direction – the direction of sewage leaving the house and going out to the street.  So under normal conditions sewage from the house flows out to the street.  Often there are two valves built into the system.

But if there’s a heavy rain and the sewer gets overwhelmed, and if that sewage then wants to flow from the city sewer back into the house, then that valve will close automatically and prevent sewage from entering the house.  Problem solved – almost.

When this happens the home’s residents wouldn’t be able to use any water, because there’s nowhere for it to go – the valve is closed and blocked.  But instead, an overflow opening is installed and the drain sewage from the house would come out of this overflow spot and into the pit, where it would flow into another smaller pit with an ejector pump.  An ejector pump is quite powerful and it can grind up the solid waste that might be present in the sewage.  The pump then pumps this overflow sewage up and over, past the backflow valve, and into the city’s sewer drain.  This allows the residents to continue using all of their plumbing fixtures.

Keep in mind that this system is for sewage only – the drain water from your sinks and tubs and showers and from your toilets.  It’s not for groundwater.  Even with this type of flood control system it’s possible for the ground to become saturated from rain, and that water can still find its way through the foundation wall or up through the floor slab and into your basement.  Solving the problem of groundwater is another issue.