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Home / Code Guides / Water Heater Installation

Water Heater Code — T&P Valve, Discharge Pipe, Drain Pan & Strapping

Water heater inspections turn on four things: the relief valve, where its discharge pipe ends, the pan under the tank, and whether the tank is strapped. Almost every correction notice is one of those four.

RequirementModel Code StandardSection
Relief valveThe temperature and pressure relief valve must open at no more than 210°F and at a pressure at least 25 psi above system pressure but not over 150 psi, with the temperature element in the top 6 in. of the tankIRC P2804.3, P2804.4
Nothing in the wayNo check valve or shutoff may be installed between the relief valve and the tank, or in the discharge lineIRC P2804.6
Discharge pipingDischarge piping must run full size to an approved point, terminate no more than 6 in. and no less than two pipe diameters above the receiving surface, discharge through an air gap in the same room as the heater, and end without threadsIRC P2804.6.1
Drain panWhere a leak would damage the structure, the heater sits in a pan of galvanized or aluminum sheet at least 0.0236 in. thick, or plastic at least 0.036 in.IRC P2801.6
Pan drainThe pan is at least 1-1/2 in. deep with a drain of at least 3/4 in., though a replacement heater is excepted where no pan drain previously existedIRC P2801.6.1
Seismic bracingIn Seismic Design Categories D0, D1 and D2, and for townhouses in category C, the tank is braced at the upper and lower third of its height to resist one-third of its operating weightIRC P2801.8
Garage elevationIn a garage, an ignition source must sit at least 18 in. above the floor unless the appliance is listed as flammable-vapor-ignition resistantIRC P2801.7

Worth knowing

  • The pan-drain exception is the most-missed line in the chapter. Swapping a heater in a location that never had a pan drain does not oblige you to add one — but it does not excuse the pan itself.
  • Mid-tank strapping does not comply. The code asks for restraint at the upper and lower thirds, which is two straps at specific heights, not one strap around the middle.
  • The IRC sets no general maximum water temperature at the heater. The 140°F and ASSE 1017 mixing-valve requirements people cite are conditional, attaching to solar preheat and to combined space-heating systems, and the limits that protect bathers live in the fixture chapter.
  • A water heater in a bedroom or bathroom is not flatly prohibited. A fuel-burning unit needs a sealed enclosure with combustion air from outside, direct-vent appliances are exempt, and the fuel-gas chapter lists further exceptions.
  • Chapter 28 was renumbered for the 2024 edition, moving the pan requirement from P2801.6 to P2801.5. Some third-party pages labeled 2021 already print the 2024 numbers.
Sections cite the 2021 International Residential Code and 2023 National Electrical Code as model standards. This is BuildSpec’s own summary — not ICC or NFPA text; read the authoritative language at codes.iccsafe.org. Your state may be on a different edition with amendments — check your jurisdiction page or get an Address Report.
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