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Guide

Backwater valve or overhead sewer? How to choose

Both protect a basement from sewer backups. Which one fits depends on how you use the basement, how the house is plumbed, and what your municipality supports.

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Questions that decide it

Decision guide
QuestionLeans toward a valveLeans toward an overhead sewer
Do you need upper-floor drains during storms?No — you can pause water useYes
Basement bathroom or kitchen?Few or noneYes, several fixtures
Comfort with a pump and power dependence?Prefer no power neededFine with a pump and backup
Municipal program?Program covers valvesProgram covers overhead sewers
Sealed ejector pit with discharge piping rising to an overhead sewer line
Illustration

Living with a 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.
  • When it is closed during a surcharge, water you use inside has nowhere to go — avoid running water during heavy storms.
  • Keep the access cover clear; clean and inspect per the manufacturer.

Living with an 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.
  • The ejector needs power; consider backup power or avoid basement fixtures during outages.
  • Test the pump and alarm periodically.

Local programs

See the comparison of municipal programs on backwater valves & overhead sewers — Oak Park, Schaumburg, Elmhurst, Joliet and Des Plaines are covered.

What to ask a provider

  • Will you camera-inspect the building sewer first?
  • Which fixtures will be protected, and which will not?
  • Who pulls the permit, and does the design meet program rules?
  • What maintenance does it need, and how will I access it?

Frequently asked questions

Can I install both?

Some designs combine an overhead sewer with a check valve. A provider can explain what fits your house and code.

Does either stop groundwater?

No. Groundwater is handled by drain tile and a sump pump.

Related

Sources

  1. Metropolitan Water Reclamation District — Understanding Your Sewer Official / primary
  2. City of Chicago DOB — Blocking Rainwater and Preventing Sewer Backup Official / primary

Information can change; official sources control.

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