Commercial plumbing repairs: tenant or landlord responsibility?

Commercial leases are not standardized the way residential leases often are. Two businesses in the same building can have very different repair duties because they signed different lease structures. That is why a plumber, a property manager, or even another tenant cannot tell you who pays just by looking at the leak.

The three common structures are triple-net (NNN), gross (full-service), and modified gross. Each one allocates costs differently, and the plumbing duty usually follows the same logic as the rest of the operating costs. Once you know which type you have, you still need to read the specific language, because landlords and their attorneys often customize the standard clauses.

A net lease shifts costs that a gross lease keeps with the owner. As the Cornell Legal Information Institute puts it, a net lease is "a lease in which the lessee pays rent plus property expenses, like taxes and insurance." That cost-shifting principle is the heart of why your lease type matters so much for a repair bill.

A triple-net lease asks the tenant to pay base rent plus the three "nets": property taxes, building insurance, and maintenance. Because the tenant is already carrying maintenance, most NNN leases put day-to-day interior plumbing and the systems that serve the leased space on the tenant. That commonly includes things like fixtures, the sink and restroom plumbing inside your suite, the water heater that serves your space, and clearing a clogged drain that you caused.

The landlord, in a typical NNN deal, keeps the items that protect the building as a whole. As Holland & Knight explains, "In a triple net lease, the tenant is responsible for paying property taxes, building insurance and maintenance costs in addition to the base rent." The same structure usually leaves the landlord holding structural elements, the roof, the building foundation, the exterior, and central or shared systems such as a main water line serving multiple tenants.

So a rough rule of thumb for NNN is this: if the plumbing problem is inside your four walls and serves only you, expect it to be yours. If it is a central, structural, or building-wide system, expect it to be the landlord's. That said, this is only a starting point. The actual division is set by your lease, and the label NNN alone does not decide a single repair.

A gross lease, sometimes called a full-service lease, works the opposite way. The tenant pays one bundled rent, and the landlord uses that rent to cover operating costs, including taxes, insurance, and maintenance. Under this structure the landlord usually carries plumbing repairs and general upkeep, because the landlord is the party responsible for the building's operating expenses. Holland & Knight describes a gross lease as one where "the tenant pays a fixed rent amount, and the landlord is responsible for paying all property expenses."

A modified gross lease sits between the two. It splits costs, and the way it splits them is negotiated deal by deal. A modified gross lease might keep structural and major systems with the landlord while passing some interior or routine costs to the tenant through a CAM (common area maintenance) charge. Because the split is custom, two modified gross leases in the same market can read very differently.

This is why the lease label is only the headline. The U.S. Small Business Administration advises tenants to understand the full cost and terms before signing, noting that a commercial lease "is legally binding and personally obligates you and sometimes your business to its terms for a specific period of time." The practical takeaway: do not assume the structure name settles your plumbing duty. Confirm it in the text.

The structure tells you the general pattern. The maintenance and repair clause and the CAM clause tell you the real answer. These are the sections that name, in writing, who fixes what and who pays. When a dispute reaches an attorney, those clauses are the first thing they read.

Look for a few specific things in your lease:

• The repair clause. It often divides duties into tenant repairs and landlord repairs, and it may carve out structural, roof, and exterior items for the landlord while assigning interior systems to the tenant.
• The definition of the premises. Whether a pipe is "inside" or "outside" your leased space can hinge on how the lease defines the boundary of the premises.
• The CAM clause. This controls which shared or building costs get passed back to tenants and in what proportion, which can pull a "landlord" repair onto your bill indirectly.
• Exclusions and caps. Some leases cap how much of a capital repair can be charged to tenants, or exclude certain replacements from CAM entirely.

Because these clauses are negotiated, the only reliable way to know your duty is to read them, ideally before you sign. A lease is a contract, and as the Legal Information Institute notes, it is "a contract by which one party conveys land, property, services, etc., to another for a specified time." The terms inside that contract, not a generic rule, control the outcome.

Even with a clear lease, some situations cause real disputes. A few recurring gray areas are worth flagging:

• A clog versus a failed main. A drain you clogged with grease or debris is usually a tenant problem. A collapsed or failed building main that serves several units is usually a landlord problem. The hard cases sit in between, such as a backup that could be tenant misuse or an aging shared line.
• The grease interceptor. In a restaurant, who pays to install, pump, and repair the grease interceptor or grease trap is a frequent fight. Some leases assign it to the tenant as equipment serving their use. Others treat the underground interceptor as a building fixture. The stakes are real: the U.S. EPA reported that grease was the single largest cause of reported sewer blockages, at 47 percent, so a neglected interceptor can become an expensive backup that triggers exactly the tenant-versus-landlord dispute this clause is meant to prevent. Check the clause before you open.
• Capital replacement versus routine repair. Replacing a worn fixture is routine. Replacing an entire failed system is capital. Leases often treat these differently, and CAM caps may apply to one and not the other.

When something goes wrong, document it. Photograph the problem, note the date and time, and keep copies of any plumber's findings. Report the issue to your landlord or property manager in writing, not just by phone, so there is a record of when you gave notice. If you and the landlord disagree on who pays, get the resolution in writing before work proceeds. Clear records turn a he-said-she-said dispute into a simple matter of reading the lease and the timeline.

This page is general information, not legal advice. Lease language varies, and Arizona law and your specific contract control the result. For a clean answer about your own space, have a qualified commercial real estate attorney review your lease and the repair and CAM clauses before you commit to a repair or a payment.

If you need fast, documented commercial plumbing work in metro Phoenix, HQ Plumbing & Air handles repairs and provides written findings you can share with your landlord or property manager. For a related but different question about residential responsibility, where the issue is the city versus the homeowner rather than tenant versus landlord, see our page on who is responsible for the sewer line in Phoenix.