An installed conventional septic system costs $3,500 to $8,500 on HomeGuide's national pages, and a replacement drain field $3,000 to $15,000. Chicago itself is entirely on city sewer, so septic work is on rural and large-lot properties at the edges of the suburbs.
Each dollar figure below is a national range published by HomeGuide, and none of them is a quote from us. Chicago blue clay, alley access, buried debris from old buildings and the haul to a dump site are what really set the cost of a job here. We read every HomeGuide page used here in October 2026.
What does a new septic system cost in the Chicago suburbs?
A new septic system in the Chicago suburbs is priced from HomeGuide's national figures: $3,500 to $8,500 conventional, $4,000 to $15,000 alternative and $15,000 to $50,000 or more engineered. A 1,000-gallon tank by itself costs $1,000 to $1,500 of that. Slow-draining clay till is why many lots here need more than a basic system.
What does replacing a seepage field or drain field cost?
Replacing a seepage field or drain field costs $3,000 to $15,000, around a $7,900 national average, by HomeGuide. Saving an old field with repairs runs $1,000 to $5,000; starting over with a new tank and field runs $4,500 to $20,000.
How can I tell my seepage field is failing?
You can tell a seepage field is failing when the ground over it is wet or greener than the rest, the yard smells of sewage, drains are slow, pipes gurgle or sewage backs up. Have the tank pumped and inspected first; HomeGuide puts pumping at $300 to $700. Clay soils fail first in wet springs.
Is a perc test needed, and will my land support a septic system?
Yes, a soil test is needed before a septic system can be designed, and HomeGuide puts a perc test at $600 to $2,000. Heavy clay till common around Chicago drains slowly, so many sites need a larger field or a different system type.
When is a mound system needed, and what does one cost?
A mound system is needed where the natural soil is too tight, too thin or too wet for a regular field, and HomeGuide puts mounds at $25,000 to $50,000 or more. An aerobic treatment unit, $20,000 to $40,000 or more, is the other common choice on a difficult lot.
What does it cost to replace a collapsed septic line on a rural Chicago-area lot?
Replacing a collapsed or broken septic line to the tank costs $40 to $180 a foot, or $1,600 to $7,200 on average, using HomeGuide's new sewer line figures. A camera inspection finds the failed section first.
How big a hole does a 1,000-gallon tank need in clay, and where is my septic lid?
A 1,000-gallon tank needs a hole wider than the tank on all sides, with the depth set by the design. HomeGuide gives no figure for the hole itself. To find a buried lid, ask the county health department for the permit records, then probe where they show the tank.
Can I connect to a public sewer instead of fixing my septic?
You can connect to a public sewer instead of fixing a septic system where a main is close enough and the village or sanitary district allows the connection. Converting from septic to sewer costs $3,000 to $15,000 in HomeGuide's figures, plus a hookup fee of $1,000 to $15,000.
Who issues septic permits around Chicago?
The Cook County Department of Public Health reviews and approves private sewage disposal systems throughout Cook County except in Barrington Hills, Inverness, Palos Park and South Barrington, which handle their own. In DuPage, Will and other collar counties, the county health department handles it. The Illinois Department of Public Health licenses private sewage disposal installation contractors. We dig under the approved design and do not design systems.
For a number on your own Chicago-area property, call or text (872) 201-3760. We look at the lot, then send the scope and the price in writing.