Who is responsible for a sewer backup in a commercial property depends on three things: what the lease says, where in the pipework the blockage is, and what caused it. There is no rule that the landlord always pays or that the tenant always pays, and commercial tenants generally have fewer automatic protections than residential ones.
This guide is general information from a plumbing point of view. It is not legal advice. What a plumber can do is establish the facts, where the blockage is and what it is made of. What those facts mean under your lease is a question for the lease itself and, if the parties disagree, for an attorney.
Stop the damage first, argue later
Before anyone works out who pays, the backup has to be stopped. Sewage is contaminated water, and every hour it sits adds to the cleanup.
What to do first
- Stop using water in the affected space: no flushing, no sinks, no dishwasher.
- Keep staff and customers out of the wet area. Treat anything the water touched as contaminated.
- Tell the landlord or property manager straight away, in writing as well as by phone.
- Take photos and video of where the water is coming up and how far it has spread.
- Ask neighboring tenants whether their drains are affected too. The answer matters later.
- Get the line cleared by a commercial plumber, and ask for a camera inspection and a written report.
Many leases require prompt notice to the landlord, and some limit what a tenant may do to building systems without consent. Read that part of your lease, or call the manager, before you authorize anything beyond stopping the backup.
The three questions that decide it
What does the lease say? Commercial leases allocate repair duties in writing, and they vary widely. Under a triple net (NNN) lease the tenant often carries most maintenance costs, sometimes including plumbing that serves only its premises. Under a gross or full-service lease the landlord usually keeps more of that. Many leases split it: the tenant maintains plumbing inside and serving only the premises, and the landlord maintains shared lines and structural or underground systems, sometimes recovering the cost through common-area charges.
Where is the blockage? Plumbing in a multi-tenant building has zones. A fixture drain and branch line inside one unit serves that tenant alone. The building drain and the main serve everyone. The lateral runs from the building to the public sewer. The location often decides which lease clause applies.
What caused it? A blockage of grease, wipes or kitchen solids traced to one tenant’s use is treated differently from a pipe that has collapsed with age or filled with tree roots. Many leases make a tenant responsible for damage it causes, wherever in the system the damage shows up.
All three have to be answered. A blockage in a shared line might be the landlord’s to repair and still be charged back to the tenant whose grease caused it.
Common scenarios and how they tend to be handled
The table shows how these situations are commonly handled. It is a general picture, not a statement of what your lease provides.
| Scenario | What a plumber typically finds | Commonly falls to | What usually decides it |
|---|---|---|---|
| One unit backs up, neighbors are fine | Blockage in that unit’s fixture or branch line | Tenant | Lease clause on plumbing serving the premises |
| Several units back up at once | Blockage in a shared building drain or main | Landlord, often recovered through shared charges | Lease clause on common systems |
| Shared line blocked by one tenant’s grease | Grease in the common line downstream of a kitchen | Disputed. Often charged back to that tenant | Evidence of the source, plus the lease’s damage clause |
| Roots or a collapsed pipe under the lot | Structural defect in the lateral | Landlord in many leases, tenant under some NNN leases | Lease clause on structural and underground systems |
| Backup from the public main | Blockage or surcharge in the city or district sewer | The sewer agency, subject to its claims process | Where the blockage is relative to the property boundary |
| Pre-existing defect found soon after move-in | Old damage, heavy scale, a sag | Often argued to be the landlord’s | Condition at lease start and any inspection record |
The third and sixth rows are where most disputes start, and both turn on evidence.
What a plumber can establish
A plumber cannot tell you what your lease means. A plumber can give you facts that make the lease question answerable.
Location. A camera inspection measures how far from the access point the blockage or defect is. A locator marks that point on the ground or the floor. You then know whether it sits inside one unit, in a shared line, in the lateral or beyond the property.
Cause. The debris and the footage show whether the blockage was grease, paper products, a foreign object, roots, scale or a broken pipe. Ask the plumber to photograph what comes out of the line.
Condition. The recording shows whether the pipe is sound, or whether there are cracks, offsets or a sag that will cause the next backup. That separates a one-off blockage from a pipe that needs repair.
Which fixtures feed the line. In some buildings it is not obvious which units connect where. Dye testing or running the camera from different access points can show it.
Ask for all of this in a written report with the video file. A line on an invoice reading “cleared main line” proves almost nothing. We describe what a proper survey contains in sewer camera inspection cost for commercial properties.
Documentation that helps both sides
Disputes over a backup are usually settled by whoever kept records. These are worth having whether you are the landlord or the tenant.
- The lease, including any exhibits on maintenance and any amendments
- The date and time the backup was noticed, and who was told and when
- Photos and video of the backup and the damage
- The plumber’s report, camera footage and a note of where the blockage was
- Service history for the line: earlier blockages, cleanings and inspections
- Grease interceptor pumping records, for food businesses
- Any inspection done at the start of the lease
- Invoices for cleanup and repair, kept separate from each other
A tenant running a kitchen should keep interceptor and line-cleaning records as a matter of routine. If grease is found in a shared line, those records are the tenant’s best evidence of good practice, or the landlord’s best evidence of its absence.
The line between private pipe and public sewer
Sometimes neither the landlord nor the tenant is responsible, because the blockage is in the public sewer.
Where the public system starts depends on the sewer agency. In much of Sacramento County, the Sacramento Area Sewer District’s sewer ordinance says the owner has the sole responsibility for clearing stoppages in, and maintaining and repairing, the upper lateral, with the boundary typically at the district cleanout. Inside the City of Sacramento, the Department of Utilities’ design standards describe the city’s service as the cleanout near the right-of-way line, the tap and the pipe between them, with the piping from the cleanout back to the building privately owned and maintained.
In practice, if the blockage is on the public side, call the agency before paying for a repair. For City of Sacramento addresses that means 311. In SacSewer’s collection area the district’s 24-hour line is (916) 875-6730. A camera run that shows the blockage is past the property-line cleanout is the evidence to give them.
These boundaries are set by each agency and can change. Confirm the rule for your address with the agency.
Insurance is a separate question
Who is responsible under the lease and who has insurance for the damage are two different things.
Many commercial property policies exclude water that backs up through sewers or drains unless a specific endorsement has been added. Some leases require the tenant to carry certain coverage, and some include a waiver of claims between landlord and tenant for insured losses. Check your policy and your lease, and ask your broker, before assuming a backup is covered.
Keep the cost of fixing the pipe separate from the cost of cleaning up and replacing damaged property. They are often handled by different parties and different policies.
How to avoid the argument next time
Most of these disputes can be prevented when the lease is signed.
Tenants: before signing, ask for a camera inspection of the line serving the space, or ask the landlord for the last one. Read the repair and maintenance clause for the words “plumbing”, “sewer”, “underground” and “serving the premises”. Ask who maintains the grease interceptor.
Landlords: keep a recorded inspection of shared lines, and repeat it at tenant turnover. State in the lease who maintains what, down to the point where a branch line joins the building drain. Require food tenants to keep interceptor and line-cleaning records, and ask to see them.
Both: put shared lines that carry kitchen waste on a cleaning schedule. A backup that does not happen needs no one to pay for it. Our comparison of hydro jetting vs snaking explains which method keeps a grease line open.
What not to do
Do not delay stopping the backup while the parties argue. The damage keeps growing, and delay can weaken a tenant’s position and an insurance claim.
Do not let the only record be a phone call. Notice in writing, with a date, is what leases usually require.
Do not rely on a general rule you read online, this page included. Residential habitability rules that require a landlord to keep plumbing working do not automatically apply to commercial leases.
Do not have the line repaired, as opposed to cleared, without telling the other party, unless the lease clearly makes it yours to repair.
Frequently asked questions
Is the landlord or tenant responsible for a sewer backup in a commercial building? It depends on the lease, the location of the blockage and its cause. Commonly, a tenant handles blockages in plumbing serving only its space, and a landlord handles shared and underground lines. Leases can change either of those, and NNN leases often move more onto the tenant.
What if another tenant caused the backup in my unit? A camera inspection and the debris removed can show where the blockage was and what it was made of. If it traces to another tenant’s use, many leases let the landlord charge that tenant. How your own losses are recovered depends on your lease and your insurance.
Does landlord vs tenant plumbing responsibility change with a triple net lease? Often, yes. NNN leases typically shift maintenance costs to the tenant, and some include plumbing and even underground lines serving the premises. The wording differs from lease to lease, so read the maintenance clause.
Can a plumber tell who is at fault for a sewer backup? A plumber can establish where the blockage was, what it was made of and what condition the pipe is in. Deciding fault and who pays is a matter for the lease and, if disputed, for legal advice.
Who pays if the city sewer main caused the backup? If the blockage was in the public sewer, the agency that owns it is responsible for clearing it, and it will have a claims process for damage. Report it to the agency promptly and keep the camera evidence.
Facts first, then the lease
A sewer backup in a leased space gets settled fastest when someone has established the facts: where the blockage was, what it was, and what shape the pipe is in. With those on paper, the lease usually gives an answer. Without them, both sides are guessing.
We clear the line, record it on camera and put the location and cause in a written report that both landlord and tenant can use. See commercial drain and sewer services, or call (866) 981-1310 and tell us which units are affected.