Do you need a permit to replace a water heater in Mesa? City Code 4-1-4(B)5 and the city FAQ

Section 4-1-4(A) requires a permit to install or replace a plumbing or gas system regulated by the code. Subsection (B) then lists work that needs no permit, and gas and electric water heaters sit in different lists:

• Gas, homes, (B)3(c). "Replacement of gas water heating appliances of equal or less Btu/cfh rating," with minor connection changes, in R-1 through R-5 occupancies, manufactured homes and recreational vehicles, where the appliance serves an individual dwelling unit.
• Gas, tenant spaces, (B)3(e). The same equal-or-lesser Btu/cfh exemption in A-2, A-3, A-4, B, E, F-2, M, S-2 and U occupancies where the appliance serves an individual tenant space.
• The gas utility condition. Both gas exemptions apply only "provided the serving Gas Utility is notified prior to the appliance being energized." That notice is a condition written into the code, not just advice.
• Electric, homes and tenant spaces, (B)5(c) and (d). The same exemption for electric water heaters of equal or lesser amperage, in the same two settings.
• State-regulated units, (B)5(e). Equal replacement of boilers and water heaters regulated by the State of Arizona is exempt, except for work outside the state's scope in industries, premises or activities regulated by Mesa City Code Title 8, Chapters 1 and 4.

The city's Residential Construction FAQ says the same in practice. It lists "No Permit Required" for residential replacements of gas and electric water heaters of equal or lesser rating using a like-for-like model, and "Permit Required" for replacing a traditional storage gas water heater with a tankless or on-demand gas water heater.

Two other parts of 4-1-4 apply. Under (B), an exemption does not authorize work that violates the chapter or the technical codes. Under (C), if a replacement that needs a permit has to happen in an emergency, the permit application is due within the next working business day.

• Like for like. The same type and fuel, and equal or lesser rating, than the unit being replaced.
• Btu/cfh and amperage rating. For gas heaters, the input rating. For electric heaters, the current draw. A higher rating is not covered by the exemptions.
• Tankless conversion. Swapping a storage tank heater for an on-demand unit, which usually changes gas sizing, venting and water connections.
• Individual tenant space. One tenant's suite in a larger building, as opposed to a whole-building central plant.

Owners and contractors replacing water heaters in Mesa homes, and building operators replacing them in single tenant suites. A central boiler plant or an industrial facility regulated under Title 8 is a different question, because (B)5(e) carves out work in those settings.

A leaking tank in a house. The owner has a licensed plumber replace a 50-gallon gas storage heater with the same type in the same closet. It is a like-for-like swap at the same Btu rating, so 4-1-4(B)3(c) exempts it. The condition is that the serving gas utility is notified before the appliance is energized.

A tankless upgrade. The same owner decides to go tankless. That conversion is the case the city names as needing a permit, and the gas line, venting and water connections all get reviewed.

The edge case. A restaurant suite replaces its gas heater with an equal-Btu unit that serves only that suite. That is exempt under (B)3(e) with the gas utility notice. It flips if the heater serves several tenants or the whole building, if the new unit has a higher Btu/cfh rating, or if a storage unit becomes tankless. Each of those needs a permit. Mesa Permit Services at 480-644-4273 can confirm a borderline case before the work starts.

1. 1Write down the old unit's fuel, size and rating, and compare it with the new one.
2. 2If it is like-for-like in a home or single tenant suite, plan to skip the permit, but notify the gas utility before a gas unit is energized.
3. 3If you are converting to tankless, apply for the permit before the work.
4. 4Have the installer follow the city's checklist items, including the temperature and pressure relief line termination, the drain pan and drain line, the required height above an ignition source and combustion air.
5. 5In an emergency that needs a permit, apply by the next business day.

• "No permit means no rules." The code still applies, and the installer is responsible for meeting it.
• "Bigger is the same as like-for-like." A higher rating leaves the exemption behind.
• "Tankless is just a new heater." The city lists storage-to-tankless gas conversion as needing a permit.
• "The gas utility only matters for new gas lines." Code 4-1-4(B)3(c) and (e) make the exemption conditional on notifying the serving gas utility before the appliance is energized.