Sump Pump and Backwater Valve Requirements by State
Applies to one- and two-family residential construction. Local plumbing officials have the final say on whether your specific elevation relative to the sewer triggers a backwater valve — this guide explains the rule, not your address's number.
Unlike most of the "by state" topics on this site, the backwater valve rule isn't a blank the model code leaves for a jurisdiction to fill in — it's a real, automatic, elevation-based trigger built directly into the IRC and IPC. If any plumbing fixture in your home sits lower than the top of the nearest upstream manhole cover in the public sewer, the code already requires a backwater valve, everywhere the model code is adopted, with no local decision needed.
Sump pumps are a different story entirely. Despite how common they are in basements across the country, there is no general national code requirement to install one — the only explicit sump mandate in the IRC applies specifically to wood foundations, not the ordinary poured-concrete or masonry basements most homes actually have. Where sump pumps show up in code at all, it's mostly about what happens once you have one: pit size, discharge location, and GFCI protection on the circuit.
A handful of states and cities — Chicago being the best-known case, but not a statewide Illinois law — amend or go beyond the baseline in ways that matter a lot to anyone finishing a basement or dealing with sewer backup.
Whether a sump pump is code-required or just a smart precaution in your area, sizing it correctly comes first — undersized pumps are a common cause of basement flooding during heavy storms. Free, no signup.
The National Rule: An Elevation Trigger, Not a Blank to Fill In
Both the IRC and IPC set the same underlying rule in nearly identical language: if a plumbing fixture sits below the elevation of the next upstream manhole cover in the public sewer, it has to be protected by a backwater valve. Above that elevation, a valve isn't required — and if one is installed anyway, it has to be a normally-open type so it doesn't block normal drainage. This is confirmed unchanged in the current 2024 editions of both codes.
| Requirement | What it says | Code section |
|---|---|---|
| When a backwater valve is required | Fixture is below the next upstream public-sewer manhole cover elevation | IRC P3008.1 / IPC 714.1 |
| When one is prohibited from serving | A fixture above that elevation may not discharge through a backwater valve (new construction) | IRC P3008.2 / IPC 714.1 |
| Material standard | Must comply with ASME A112.14.1, CSA B181.1, or CSA B181.2 | IRC P3008.3 / IPC 714.2 |
| Access | Must be installed where the working parts are accessible | IRC P3008.4 / IPC 714.3 |
Sump Pumps: Not a National Mandate — Except for Wood Foundations
Despite how standard a sump pump feels in basement construction, no model-code section requires one for a typical concrete or masonry foundation. The single explicit exception is a permanent wood foundation: where soil isn't well-drained Group I soil, the IRC requires a sump at least 24 inches in diameter (or 20 inches square), extending at least 24 inches below the basement floor, to drain the porous gravel layer beneath a wood foundation. For everything else, whether you have a sump pump comes down to local groundwater conditions, your foundation drain's ability to drain by gravity, and — where the code does weigh in — how the sump has to be built and where it's allowed to discharge once you have one.
| Item | Requirement | Section |
|---|---|---|
| Wood-foundation sump size | 24" diameter minimum (or 20" square), extending 24" below the basement floor | IRC R405.2.3 |
| Standard sump pit (where installed) | 18" diameter, 24" deep minimum unless otherwise approved | IPC 1113.1 |
| Foundation drain (general) | Must discharge by gravity or mechanical means to an approved drainage system | IRC R405.1 |
Where Sump and Storm Discharge Is — and Isn't — Allowed to Go
The plumbing code is much more specific about discharge than about whether you need a sump pump in the first place. Storm water and subsoil drainage generally can't be routed into a sewer intended for sanitary sewage only, since that overloads treatment plants and any combined sewer during storms — the classic cause of the neighborhood-wide backups that drove cities like Chicago to regulate this so heavily. For a one- or two-family home, the code permits discharging to a flat area like a lawn or the street, as long as the water flows away from the building, or to an approved storm sewer or dry well.
Illinois: A Chicago Ordinance, Not a State Law
Chicago is the best-known name in backwater-valve conversation in the U.S., but it's important to get the distinction right: this is a City of Chicago Municipal Code requirement, not an Illinois state law. Illinois's own state plumbing code administrative rule that once addressed backwater valves (77 Ill. Adm. Code 890.550) is currently listed as repealed, and no other statewide Illinois mandate was found. Within Chicago, the ordinance language protects fixtures below the next upstream manhole with a backwater valve, in the same spirit as the model code, and separately allows flood-control measures and sewage ejectors in areas with documented sewer backup history, subject to the water management commissioner's approval. Claims of a citywide overhead-sewer mandate or a standing homeowner rebate program for backwater valve installation could not be confirmed as currently active — Chicago has run pilot programs and a city council committee was still analyzing a NEW proposed program as of 2026, which on its own indicates no funded citywide rebate exists yet.
States and Cities That Amend the Baseline
Beyond Chicago, several other jurisdictions have written their own version of the backwater-valve rule, either tightening the elevation trigger or changing the compliance options.
| Jurisdiction | How it differs from the base rule | Basis |
|---|---|---|
| Wisconsin | State-level rule requires EITHER a backwater valve OR a sump with pumping equipment for a drain subject to backflow — a genuine statewide amendment, not just a city ordinance | Wis. Admin. Code SPS 382.30 |
| New York City | Fixtures in a mapped flood hazard area are automatically deemed "subject to overflow" and must meet ASCE 24's backwater-valve standard, beyond the base manhole-elevation trigger | NYC Plumbing Code §715.1 |
| Philadelphia | Replaces the manhole-cover reference point with the elevation of the fresh-air-inlet termination | Philadelphia Plumbing Code P-714.1 |
| Pima County, AZ | Requires a valve where the finished floor is within 12 inches above the next upstream manhole cover — a wider safety margin than the base "below" trigger | 2024 IPC local amendment |
| Kyle, TX | Requires backwater valves for all new construction AND retrofits, not just fixtures below the manhole elevation | City of Kyle IPC amendment |
Electrical: GFCI Is Required, Battery Backup Is Not
Since the 2020 NEC, a sump pump's circuit (150 volts or less to ground, 60 amps or less, hard-wired or cord-and-plug) needs GFCI protection — a real, dated electrical-code change worth knowing about if you're replacing an older pump on an ungrounded or non-GFCI circuit. A handful of states have adopted exemptions letting certain pumps skip this protection, so confirm with your local electrical inspector rather than assuming national uniformity. What the code does NOT require anywhere verified in this research is a battery or water-powered backup system for a sump pump — that remains a strong practical recommendation (a power outage during a storm is exactly when a sump pump is needed most), never a code mandate.
Flood Zones and Insurance: Less Specific Than You'd Expect
The federal flood insurance program's own regulation requires that new and replacement sewage systems in flood-prone areas "minimize or eliminate infiltration of flood waters" — general performance language that doesn't name a backwater valve or sump pump specifically, leaving the actual compliance method up to the adopted local plumbing code. No state insurance regulator or insurer-published premium discount specifically tied to installing a backwater valve or backup sump pump was found in this research — if your insurer or state offers one, it isn't something documented widely enough to cite here with confidence.
Standards & Citations
| Standard | Code / Section | Requirement |
|---|---|---|
| IRC Backwater Valve Trigger | 2024 IRC P3008.1 | A backwater valve is required where a fixture's flood level rim sits below the next upstream public-sewer manhole cover. |
| IPC Backwater Valve Trigger | 2024 IPC 714.1 | Same trigger, keyed to finished floor elevation rather than fixture rim height. |
| IRC Wood Foundation Sump | 2024 IRC R405.2.3 | The only explicit national sump mandate — applies to permanent wood foundations, not standard concrete/masonry. |
| Chicago Backwater Valve Ordinance | Chicago Municipal Code §18-29-715.1 | City-level ordinance, not a statewide Illinois law. |
| Wisconsin Backwater Valve or Sump | Wis. Admin. Code SPS 382.30 | Statewide amendment allowing a backwater valve OR a sump with pumping equipment. |
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Frequently Asked Questions
Is a backwater valve required by code?
Yes, but only in a specific situation: both the IRC and IPC require one wherever a plumbing fixture sits below the elevation of the next upstream manhole cover in the public sewer. This is an automatic, elevation-based trigger built into the model code itself — not something left to local jurisdictions to decide from scratch, though many cities and states have amended the baseline to be stricter (Chicago, Philadelphia, and several counties among them).
Is a sump pump required by code?
Generally, no. There is no national code requirement for a sump pump in an ordinary concrete or masonry foundation. The one explicit exception is a permanent wood foundation, which requires a sump of specific dimensions to drain the gravel layer beneath it. Wisconsin is a notable state-level exception, requiring either a backwater valve or a sump with pumping equipment on drains subject to backflow.
Does Chicago require backwater valves statewide in Illinois?
No — this is a common misconception. Chicago's backwater valve requirement is a City of Chicago Municipal Code ordinance, not an Illinois state law. Illinois's own state administrative rule that once addressed backwater valves is currently listed as repealed, and no statewide Illinois mandate was found.
Where can a sump pump discharge?
Generally not into a sanitary-only sewer — that's prohibited because it overloads treatment plants and combined sewer systems during storms. For a one- or two-family home, the plumbing code permits discharge to a flat area like a lawn (as long as water flows away from the building) or to an approved storm sewer or dry well. There's no national minimum setback distance from your foundation or property line, so check your local ordinance.
Does a sump pump need GFCI protection?
Since the 2020 NEC, yes — a sump pump's circuit needs GFCI protection. If you're replacing an older pump that was never on a GFCI circuit, this is worth checking with an electrician, since a handful of states have adopted exemptions for certain pump types. Battery or water-powered backup power for the pump is a strong practical recommendation, especially given that power outages often coincide with the storms that cause flooding, but it is not a code requirement anywhere verified in this research.
Where do these requirements come from?
The IRC and IPC backwater-valve sections, the wood-foundation sump requirement, and the federal flood insurance regulation were all read directly from the primary source — ICC Digital Codes and the official eCFR. State and city amendments are cited to their own government or municipal code sources; sources are cited by section for every requirement on this page.
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