Check valve installation in Chicago can mean two different things, and they should not be confused.
- Sump pump check valve: installed in sump-pump discharge piping to limit pumped water from falling back into the basin.
- Sewer backwater valve: installed on the sewer/drainage side where code and plumbing layout allow, to help limit reverse sewer flow into low basement fixtures.
The right valve depends on which pipe is sending water backward.
Sump Pump Check Valve vs. Sewer Backwater Valve
| Valve | Where it belongs | Problem it addresses |
|---|---|---|
| Sump pump check valve | Sump-pump discharge line | Pumped groundwater falling back toward the sump basin |
| Sewer backwater valve | Building drain / sewer branch where applicable | Reverse sewer flow toward low fixtures |
If water falls back into the sump pit immediately after the pump stops, look at the sump discharge system. If water comes up through a floor drain, toilet, shower, or laundry fixture, look at the sewer side.
What a Sump Pump Check Valve Does
A sump-pump check valve limits reverse flow in the discharge line after the pump shuts off.
Without effective backflow control, some of the water already lifted out of the basin can fall back and force the pump to restart sooner.
Current Zoeller installation guidance instructs installers to use a check valve and union in the discharge line. Zoeller also identifies a stuck-open or missing check valve as one possible cause of a pump starting and stopping too often.
Possible signs of a sump-discharge check-valve problem include:
- A noticeable rush of water back into the pit after shutdown
- The pump restarting shortly after it stops
- Frequent cycling during otherwise moderate inflow
- Visible leakage around the valve or fittings
- A valve that no longer closes consistently
For broader discharge problems, use sump pump discharge line service.
Chicago Code for Sump / Storm Pump Check Valves
Chicago’s current storm-sump piping provision requires discharge piping to include a full-flow check valve. The same section states that discharge piping and fittings must be the same size as or larger than the pump discharge tapping.
Duplex pump systems have additional valve requirements on each pump discharge.
Current code language is available in Chicago Plumbing Code Section 18-29-1111.3.4.
A Loud Check Valve Is Not Automatically a Failed Check Valve
A loud thump when the pump stops can be water hammer—the sound created when flow reverses and the check valve closes.
Zoeller’s current support guidance specifically notes that this closing noise can be more annoying than damaging and suggests a quieter check-valve design when noise is the main issue.
That means noise alone does not prove the valve has failed. The more useful questions are:
- Does significant water return to the pit?
- Is the pump short-cycling?
- Is the valve leaking?
- Does the valve close consistently?
- Is the discharge piping supported and sized correctly?
Check Valve Problems That Can Mimic Pump Problems
A bad sump check valve can make a healthy pump look like it is working too hard.
For example:
- Water falls back after shutdown → pump restarts sooner
- Valve restriction → reduced effective discharge flow
- Improper installation → leaks or unstable operation
- Backflow plus a small basin → frequent cycling
If the pump itself is silent, humming, or unable to lower the basin, use sump pump repair. If the valve is the isolated problem, valve service may be enough.
What a Sewer Backwater Valve Does
A sewer backwater valve is a different device. It is intended to provide a mechanical barrier against reverse sewer flow toward low fixtures.
Sewer-side warning signs include:
- Floor drain backup
- Gray or dirty water
- Sewage odor
- Basement toilet bubbling or backing up
- Shower or laundry fixture backup
- Multiple low fixtures affected together
A sump-pump check valve will not solve those symptoms.
For the broader sewer-side assessment, use sewer backup prevention.
Current Chicago Backwater-Valve Rule
Chicago’s current plumbing code does not say that every basement should simply receive a backwater valve.
The code states that a backwater valve is installed for plumbing fixtures where the overflow rim of the lowest fixture is below the next upstream manhole in the public sewer. Fixtures with flood rims above that manhole are not to discharge through the backwater valve.
The current code also requires access to the working parts for service and repair.
See Chicago Plumbing Code Section 18-29-715.1 and Section 18-29-715.6.
Why Backwater-Valve Placement Matters
A sewer backwater valve is not simply inserted wherever access is easiest.
The assessment needs to consider:
- Lowest vulnerable fixture
- Fixture flood-rim elevation
- Relationship to the next upstream public-sewer manhole
- Which fixtures belong on the protected branch
- Building-drain layout
- Cleanout and service access
- Existing ejector or flood-control equipment
- Permit and inspection requirements
The valve must remain accessible because moving parts can require inspection, cleaning, and repair.
Backwater Valve vs. Overhead Sewer
A backwater valve is one sewer-backup protection method. An overhead sewer is a larger plumbing redesign.
| Option | Basic function | Typical consideration |
|---|---|---|
| Backwater valve | Mechanically limits reverse sewer flow | Fixture elevations and branch layout must be suitable |
| Overhead sewer | Reconfigures vulnerable below-grade drainage so wastewater is lifted before entering the building sewer | Larger project for repeated backup or vulnerable low fixtures |
| Sump pump check valve | Limits groundwater discharge from falling back into sump pit | Part of sump-pump discharge system, not sewer protection |
For larger sewer-backup projects, see overhead sewer systems.
Can You Use Plumbing Fixtures While a Backwater Valve Is Closed?
When a backwater valve closes because the sewer is pushing backward, wastewater from protected fixtures may not have its normal downstream path.
That is one reason fixture layout and valve placement matter. The operational effect depends on the design of the protected branch and the rest of the building drainage system.
During known sewer-backup conditions, unnecessary water use should be minimized.
Check Valve Installation and Maintenance
Whether it is a sump-discharge check valve or sewer backwater valve, installation quality and future access matter.
For sump-discharge valves, review:
- Correct flow direction
- Pipe size
- Union / service access where appropriate
- Leak-free fittings
- Discharge support
- Float-switch clearance
- Backflow after shutdown
For sewer backwater valves, review:
- Code-appropriate placement
- Protected fixtures
- Access for inspection and service
- Valve movement and cleanliness
- Building-drain condition
- Permit requirements
Check Valve Installation Cost
Cost depends heavily on which valve is being discussed.
A sump-pump discharge check-valve replacement is a much smaller scope than installing a sewer backwater valve beneath a basement floor or as part of a larger flood-control project.
Pricing factors can include:
- Valve type and size
- Accessibility
- Existing pipe condition
- Concrete cutting and restoration
- Drain or sewer layout
- Permit and inspection requirements
- Whether additional flood-control or overhead-sewer work is needed
Chicago and Nearby Service Areas
This page focuses on check-valve and backwater-valve assessment in Chicago. Nearby service availability may also include Oak Park, Berwyn, Cicero, Forest Park, Elmwood Park, River Forest, Skokie, Evanston, Lincolnwood, Niles, Park Ridge, and Des Plaines depending on location, scope, and scheduling.
Municipal plumbing and flood-control requirements can differ. See Areas We Serve for location-specific context.
Check Valve Installation FAQ
Is a sump pump check valve the same as a sewer backwater valve?
No. A sump-pump check valve belongs in the pump discharge system. A sewer backwater valve belongs in the building drainage system where the plumbing layout and code allow.
Why does water fall back into my sump pit after the pump stops?
A failed, missing, stuck-open, or improperly installed sump check valve can allow discharge water to return. Discharge configuration can also contribute.
Does Chicago require a check valve on storm-sump discharge piping?
Yes. Chicago’s current storm-sump piping section requires a full-flow check valve in the discharge piping.
Does every Chicago basement need a sewer backwater valve?
No. Chicago’s current code ties backwater-valve protection to the elevation of the lowest fixture relative to the next upstream public-sewer manhole and specifies which fixtures may discharge through the protected branch.
Does a sewer backwater valve need maintenance access?
Yes. Chicago’s current code requires access to the working parts for service and repair.
Does a loud check-valve thump mean the valve is broken?
Not necessarily. The noise can be water hammer as flow reverses and the valve closes. Check for actual backflow, leaks, short-cycling, or inconsistent valve operation before assuming failure.
Request Check Valve / Backwater Valve Assessment
If water is returning to the sump pit, start with the sump discharge and check valve. If water is coming backward through floor drains or basement fixtures, start with a sewer-backup assessment instead.