Usually no. Maricopa County says permits are no longer required to replace an existing water heater in its jurisdiction if the work follows the manufacturer's specifications. You may still apply for a permit if you want the county to inspect it. City addresses follow city rules, and moving to a new type of heater is not covered by that line.
What does Maricopa County say about water heater permits?
The county publishes a list of Minor Permits. One group on that list is the web-issued permits, which the county describes this way: "Web issued permits are fully automated, online permits." A water heater appears in that group, with a note that changes the usual answer. It reads: "Permits are no longer required to replace an existing water heater provided the work is done in accordance with manufacturer's specifications."
The next sentence gives you a choice. It says: "However, if you wish to have Maricopa County inspect the work you may apply for a permit." So the county treats a water heater replacement as optional to permit, not forbidden to permit. You can skip the permit, or you can pay for the county's eyes on the job. Which one makes sense depends on who is doing the work and how comfortable you are with the result.
Two things about that wording matter.
First, it says "replace an existing water heater." The line is about a replacement. It does not say anything about adding a water heater where there was none, moving one to a new room, or changing from one kind of heater to another. The county page does not address those cases, so do not assume the exemption covers them. If your job goes beyond a straight swap, call the county before you start and ask.
Second, the exemption is tied to the manufacturer's specifications. That is a real condition, not a formality. The next section covers what it asks of the person installing the heater.
Does this apply to my address?
Only if the county issues permits where you live. Maricopa County Planning and Development covers unincorporated areas, which are places outside the boundaries of any city or town. If your address is inside a city, that city's building department decides, and the rules differ from one city to the next.
The differences are big enough to matter. Phoenix, for example, exempts an in-kind swap of a water heater in a one- or two-family home when a licensed contractor does the work, and it requires a permit when a homeowner does it. Our page on permits to replace a water heater in Phoenix has the details. Mesa's residential FAQ says no permit is needed to replace gas and electric water heaters of equal or lesser rating with a like-for-like model, and it requires one to replace a storage gas heater with a tankless gas unit. We cover that in our Mesa page on a tank to tankless switch. None of that carries over to the county.
To learn which side of the line you are on, look at your tax bill or mailing details for the city name, or ask the county. A wrong guess leaves you following the wrong rule.
What do the manufacturer's specifications require?
Because the exemption depends on following the manufacturer, it helps to read what a manufacturer actually asks for. We looked at the instruction manual for an A. O. Smith residential gas atmospheric vent water heater. Your heater's manual is the one that counts, so treat this as an example of the kind of items you will find, not a checklist for every model.
Local codes still apply. The manual says: "The installation must conform with these instructions and the local code authority having jurisdiction." In other words, skipping the permit does not skip the rules. The county is the code authority for an unincorporated address, and the heater still has to be installed the way the manufacturer and the code require.
The relief valve has a strict setup. The manual says the temperature and pressure relief valve must not be removed from its designated opening or plugged. It says the valve must be installed directly into the fitting made for it, pointed downward, with tubing so that any discharge exits within 6 inches above the floor or at any distance below it. It also says the discharge opening must not be blocked or reduced in size, and that excessive length over 30 feet, or more than four elbows, can restrict the flow. A relief valve that drips or is capped off is a warning sign, not a repair. Our page on a leaking pressure relief valve explains what to do.
Thermal expansion may need a tank. The manual says: "A properly sized thermal expansion tank must be installed on all closed systems to control the harmful effects of thermal expansion." It says devices such as pressure reducing valves, check valves and back flow preventers cause the water system to be a closed system. If your home has any of these, the swap may need an expansion tank that the old setup did not have. See do I need an expansion tank for how to tell.
Location matters. The manual says a heater installed where a leak could damage the structure should not go in an attic or on an upper floor if it can be avoided. When it cannot be avoided, it calls for a suitable metal drain pan piped to an adequate drain. Our page on a water heater drain pan that overflows covers the pan side.
Gas connections must be tested. For a gas heater, the manual says: "The water heater and its gas connection must be leak tested before placing the water heater in operation." It also says to check all the gas piping for leaks before lighting the heater, using a soapy water solution and never a match or open flame. This is the part of the job that is hardest to do safely by feel, and the part where an inspection or a licensed plumber earns its keep.
Should you still get a permit or an inspection?
The county leaves that to you, and there are fair reasons to go either way.
You may decide to skip the permit if a licensed plumber is doing a straight like-for-like swap and will follow the manual. The county has taken that job off the permit list.
You may decide to apply if you are doing the work yourself, if the heater is going in a tight or unusual spot, or if you want a county inspector to confirm the venting, the relief valve line and the gas connection before you rely on it. The county says it will inspect if you apply, so the option is real. Ask the county what the permit involves and what it costs at the time, because fees change and we do not quote them.
Here are some situations where you should not treat the exemption as settled:
- You are changing the kind of heater. A tankless unit in place of a storage tank changes gas sizing, venting and sometimes the electrical supply. The county wording says replace an existing water heater. Ask before you assume it fits.
- You are moving the heater. A new location means new piping, a new vent path and a new relief valve line.
- You are adding a gas line. The county lists a new gas line for a BBQ, fireplace, fire pit or pool or spa heater in a separate group of permits, so new gas work is not the same as a water heater swap. Our page on who may install a gas line in Arizona covers the licensing side.
- You are unsure whether the address is county or city. Confirm it first.
Arizona also has licensing rules for who may do plumbing work for pay. If you hire someone, you can verify the license with the steps in how to verify a plumber's ROC license. If you plan to do it yourself, can I do my own plumbing in Arizona explains what the state allows.
If you are deciding whether the heater is worth replacing at all, should I repair or replace my water heater walks through the choice. HQ Plumbing and Air can swap a water heater, set the relief valve line and expansion tank, and test the gas connection, and we will tell you up front which permit questions apply at your address.