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Service · Chicago area

Backwater valves and overhead sewers

In a combined-sewer area, heavy rain can push sewage back into the lowest drains of your building. Two main protections exist, and many suburbs help pay for them.

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Backwater valve

House sewer connection to a combined street sewer, with a backwater valveCross-section: a house with a basement floor drain connects through a private sewer lateral to a combined sewer under the street. A backwater valve on the lateral closes when water flows backward from the street sewer. GRADE BASEMENT floor drain access cover PROPERTY LINE (approx.) private side ←→ public way COMBINED SEWER rain + wastewater surcharge pushes back 1234
Diagram How a backwater valve protects a basement drain connected to a combined sewer.
  1. Basement floor drain — the lowest opening, so usually the first place sewer water appears.
  2. Private sewer lateral (building sewer) — typically the owner’s responsibility.
  3. Backwater valve — a flap that is meant to close when flow reverses; needs an access cover for cleaning and inspection.
  4. Combined street sewer — during heavy rain it can fill and back up toward buildings (MWRD).
Simplified schematic, not to scale. Actual layouts vary by building.
Sealed ejector pit with discharge piping rising to an overhead sewer line
Illustration

Overhead sewer

Overhead sewer conversion with an ejector pumpCross-section: basement fixtures drain to a sealed ejector pit. The pump lifts wastewater up to a new overhead sewer line near the basement ceiling, which exits above the old floor-level connection. Upper-floor fixtures drain by gravity to the overhead line. BASEMENT upper-floor drains (gravity) sealed ejector pit WC old low connection (plugged) to street sewer 1234
Diagram An overhead sewer keeps the building's sewer connection above the basement floor so a backed-up street sewer cannot flow in through floor-level openings.
  1. Ejector pump with check valve lifts basement wastewater up; it needs power, so outages matter.
  2. Overhead sewer line runs near the basement ceiling.
  3. Building sewer exits the wall at a higher elevation.
  4. Former floor-level openings are sealed under the design.
Simplified schematic, not to scale. Actual layouts vary by building.

Side by side

Backwater valve vs overhead sewer
AspectBackwater valveOverhead sewer
How it worksFlap closes when flow reversesSewer connection raised; basement fixtures pumped up
Needs powerNoYes (ejector pump)
During a stormAvoid using drains while closedUpper floors drain normally
MaintenancePeriodic cleaning per manufacturerPump and check valve upkeep
Typical scopeExcavation at the building sewerBasement plumbing reconfigured

MWRD describes check valves and overhead sewers as valuable home improvements that prevent sewer backups when properly installed, and advises cleaning backwater valves per manufacturer instructions.

Source: Metropolitan Water Reclamation District — Understanding Your Sewer

Local cost-share programs

Examples of municipal programs (terms change — verify)
MunicipalityProgram (as published)Page
Oak ParkSewer Backup Protection Grant, max. $3,500 (2024)Oak Park
SchaumburgOverhead sewer cost share: 50% up to $5,000, detached single-familySchaumburg
ElmhurstOverhead sewer program: 50% up to $5,000 (2023)Elmhurst
JolietOverhead sewer conversion and backflow prevention cost sharing; documented backup requiredJoliet
Des PlainesFlood rebate: 30% up to $2,000Des Plaines
ChicagoNo City-funded private valve program found at last reviewBasement flooding

Permits

Both are permit work in Chicago and in the suburbs we reviewed. Cost-share programs typically require permits, pre-approval or inspections — read the program rules before work starts.

In Chicago, most plumbing work must be done by a licensed and bonded plumbing contractor holding a City of Chicago license in addition to State licensing. In the suburbs, plumbers are licensed by the State and each municipality runs its own permits. Chicago permits · Illinois licensing

What affects the cost

We do not publish prices. Providers typically consider: depth and route of the building sewer, basement floor and finishes, number of basement fixtures, ejector and electrical work, permits, and restoration. Ask how the price is calculated before work starts.

Frequently asked questions

Which is better, a valve or an overhead sewer?

It depends on the building, how the basement is used and the sewer layout. Overhead sewers let upper floors drain during a storm but rely on a pump; valves are simpler but close the whole line while shut.

Will a backwater valve stop groundwater flooding?

No. It only blocks sewage flowing backward through the drains. Groundwater is handled by drain tile and sump pumps.

Do I need a permit?

Yes, in the jurisdictions we reviewed. Programs that reimburse the work generally require the permit too.

Related

Sources

  1. Metropolitan Water Reclamation District — Understanding Your Sewer Official / primary
  2. Village of Oak Park — Sewer Backup Protection Grant (2024 application packet) Official / primary
  3. Village of Schaumburg — Overhead Sewer Cost Share Program Official / primary
  4. City of Elmhurst — Overhead Sewer Program (2023 PDF) Official / primary
  5. City of Joliet — Overhead Sewer Conversion and Backflow Prevention Cost Sharing Program Official / primary
  6. City of Des Plaines — Flood Rebate Program Official / primary

Information can change; official sources control.

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