10 Water Heater Installation Code Requirements (2024 Guide)

Welcome to our comprehensive guide on water heater code requirements!

In this article, you'll learn:

  • Why a catch pan may be needed
  • Discharge piping requirements
  • Locations prohibited to install
  • And more!
water heater installation code requirements

When inspecting homes, I sometimes come across water heaters that have missing TPR valves and other risky issues.

When the TPR valve and discharge piping isn't up to par, it can lead to burns. Or if the water heater isn't protected from cars, it can result in severe damage.

And if you are in an earthquake or seismic zone, straps need to be installed in case of disaster. Just imagine: water heaters sometimes enter zones of extreme temperature and pressure, and building code helps prevent costly mistakes. 

Keep reading to learn our list of the top 10 water heater installation codes!

What Are Water Heater Installation Code Requirements?

Water heater installation code requirements improve home safety and help prevent water damage.

A water heater is a compact tank full of pressurized hot water. Water heaters have even been known to explode on occasion. And of course, water heaters can cause significant water damage if it leaks in a finished area.

The International Residential Code

Water heater installation code is clearly laid out in the IRC or International Residential Code in Chapter 28 - Water Heaters.

The IRC is known as a model code, and many U.S. states and countries have adopted it. Your local state may have some variation to the IRC or exceptions.

And don't forget, your local county or state will likely require a permit for a water heater installation and for it to be installed by a licensed plumber.

This article covers the most important water heater install codes in the IRC, but always check your local state because it has priority.

Read Also >> What Is The Code For Gas Fired Water Heater Venting?

10 Water Heater Installation Code Requirements

  1. A Pan Needs To Be Installed If There Is Water Damage Risk
  2. Catch Pan Should Be Made of Approved Material
  3. Prohibited Install Locations Of Water Heaters
  4. Water Heaters Need To Be Protected From Damage
  5. Water Heaters With Ignition Sources Should Be Raised
  6. Water Heaters Should Be Protected From Earthquakes
  7. TPR Valve Is Required
  8. Discharge Pipe Should Be Installed Onto TPR Valve
  9. Discharge Pipe Should Terminate To Pan, Outside, or Floor Drain
  10. Shutoff Or Check Valves Are Prohibited

Code #1. A Pan Needs To Be Installed If There Is Water Damage Risk

A catch pan should be installed underneath the water heater where leakage will cause damage.

A catch pan will collect any leaking water and prevent drywall, subfloor, wood flooring, and any other finish materials from getting damaged.

If the water heater is installed in a finished area, there should be a pan installed. If the water heater is in a garage, unfinished basement, or outside, then a catch pan is not required.

Also, if the water heater is in the attic, the water heater needs a catch pan because it may leak onto the finished ceiling below.

Read Also >> What Are The Code Requirements For Dryer Venting?

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Code #2. Catch Pan Should Be Made of Approved Material

The catch pan should be made out of No. 24 galvanized steel, plastic at least 0.9-mm thick, or other approved materials by the manufacturer.

If the catch pan is made out of plastic, and the water heater is gas-fired, then the plastic pan needs to have a flame spread index of 25 or less. Also, the smoke developed index should be 450 or less.

Code #3. Prohibited Install Locations Of Water Heaters

Water heaters are prohibited from being installed in any area if it is being used as a storage closet.

Water heaters are prohibited from being installed in bedrooms or bathrooms unless it is in a sealed enclosure. Also, combustion air cannot be taken from the adjacent bedroom or bathroom.

Read Also >> What Is The Code For Plumbing P-Traps?

Code #4. Water Heaters Need To Be Protected From Damage

Water heaters need to be protected from getting hit by cars.

If the water heater is in a garage or some area where there is risk of car damage, then it needs to have a barrier.

Code #5. Water Heaters With Ignition Sources Should Be Raised

Water heaters need to be raised above the floor on a platform if it has an ignition source.

If you have a gas or oil-fired water heater with an ignition source (open flame or spark), then the water heater needs to be raised at least 18-inches above the floor.

Sometimes flammable vapors get released by accident in homes (especially garages), and the vapors tend to stay near the floor. If the water heater creates a spark or flame, it may ignite the flammable vapor, which is why this code is required.

One exception to this code is if the water heater is flammable vapor ignition-resistant as stated by the manufacturer.

Read Also >> What Are The Code Requirements For Toilet Clearances?

Code #6. Water Heaters Should Be Protected From Earthquakes

The water heater needs to be protected from earthquakes if it is in a seismic zone.

There should be at least two straps on the top 1/3 and the bottom 1/3 of the water heater. 

Each strap should be able to handle horizontal forces of at least 1/3 the weight of the water heater. For this building code, it only applies to homes in Seismic Categories of D0, D1, D2, and townhomes in C.

Code #7. TPR Valve Is Required

water heater installation code requirements (3)

A TPR valve (temperature pressure relief) is required on water heaters to prevent an explosion.

If the pressure becomes too great in the tank, or if the temperature rises too high, then the TPR valve will release water and steam.

It can be a single 'combo' TPR valve, or the water heater is allowed to have a separate temperature relief valve and pressure relief valve.

Read Also >> What Are The Code Requirements For Range Hood Venting?

Code #8. Discharge Pipe Should Be Installed Onto TPR Valve

The TPR valve needs a discharge pipe.

Sometimes when I inspect homes, the water heater is missing a discharge pipe.

This is dangerous because if the TPR valve is released, and if someone is in the room, they can get severely burned.

Code #9. Discharge Pipe Should Terminate To Pan, Outside, or Floor Drain

The discharge pipe for the TPR valve should go outside, to a catch pan, or a floor drain.

If it terminates on the outside, the discharge pipe should be visible to homeowners.

The discharge pipe should also be adequately sloped so it will drain by gravity.

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The discharge pipe needs to terminate a maximum of 6-inches above the floor, and a minimum of 2x the pipe diameter.

Here are a few other code requirements for discharge piping:

  • Should not be directly connected to drainage system
  • There should be an air gap
  • Pipe size shouldn't be smaller than the TPR valve
  • Only a single pipe allowed (it shouldn't serve another system)
  • P-trap is not allowed
  • Threaded end is not allowed

Code #10. Shutoff Or Check Valves Are Prohibited

Check valves and shutoff valves are not allowed to be installed between the TPR valve and the termination.

Read Also >> What Is The Building Code For Bathroom Fan Venting?

Final Thoughts On Water Heater Install Codes

Water heater installation codes are essential guidance for safety.

Water heaters are pressurized tanks, and have the explosive potential to destroy an entire home. And if they leak, water heaters may cause significant flooding damage.

Probably the most important codes has to do with the requirements for the TPR valve and discharge piping. The TPR valve is an essential safety device, and the discharge piping will also prevent burns to a nearby person.

I hope you enjoyed our guide on water heater installation code.

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9 thoughts on “10 Water Heater Installation Code Requirements (2024 Guide)”

  1. Is it required to have a drain line to the outside. Not the TPR drain but the one that drains the water heater?

    Reply
  2. I’m looking at a home to buy. We did the initial viewing (new build) and we noticed the water tank is under the house (crawl space) and half of it is underground! I’m not a professional but this seemed odd to me. Can you tell me why a builder would do this and is it safe? FYI, home is in TN. Thank you!

    Reply
  3. I’ve been told by a contractor (state of Maryland) that our residential water heater flue cannot ‘by code’ exhaust alone up our ceramic chimney, and thus requires either a metal upgrade to our chimney or to have it replaced when we replace our boiler with a ‘combi-boiler’. I don’t see anything obvious in the code here or in the Maryland code.

    What am I missing?

    Reply
  4. Thanks for taking my questions.
    Are there clearance requirements between the water heater and wall?
    Is a 3/4 inch PVC line sufficient for the drain pan?
    Is the use of shark bite fittings accepted most of the time?
    Is it OK to put the water heater on a heavy wooden platform?

    Reply
    • Hey Richard,

      Yes, 3/4″ is the minimum required for the drain line and the pan itself should be at least 1.5″ deep.

      I don’t see anything specific to water heaters for clearance in the IRC but there are associated requirements in regards to easy access, general gas appliance clearances, and the vent pipe (if it is gas-fired). You can see those requirements in this IRC section here. In IRC M1306.1, it basically states to follow the appliance label and the manufacturer’s instructions in regards to clearances. I would look up your water heater manual and see what it says.

      As far as I’m aware, all SharkBite fittings are approved for electric/gas water heaters.

      In regards to the wood platform, I believe some U.S. states do not allow it such as CA. I recommend checking with local state code. I don’t see anything specific to wood platforms in the IRC. It’s probably not the best idea though if the water heater is gas-fired. Some cement board can at least be fastened on top of it.

      I hope this helped.

      Cheers,
      Arie

      Reply

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