Chapter 16
Water heaters that went under water
The questionMy water heater sat in floodwater; can I dry it out and use it again?
The short answerA flooded water heater should not be lit, switched on or used again, because two major makers say any heater that went under water should be replaced, and a third wants a qualified technician first.
By the editors of High Water at Home · Updated · about 7 minutes
Sections in this chapter
16.1 What do the makers say about a flooded water heater?
The makers say replace it. A. O. Smith's technical bulletin states its position that any water heater or boiler subjected to flooding or extensive inundation should be replaced, and adds: do not operate the appliance if any part has been under water. Bradford White's homeowner FAQ goes further: if the heater is flooded to any degree, contact a plumbing professional to replace, not repair.
Rheem's gas heater manual says do not use the appliance if any part has been under water, and to call a qualified service technician at once to inspect it and replace any part of the control system that was under water. None of the three gives a depth below which a flooded heater is fine.
| Maker or agency | What it says | Fuel |
|---|---|---|
| A. O. Smith, Technical Bulletin #0823 | Replace any heater subjected to flooding; flood voids all warranty | Gas and electric |
| Bradford White, homeowner FAQ | Flooded to any degree: replace, not repair | Gas and electric |
| Rheem, gas manual AP21831 | Do not use; technician inspects and replaces flooded control parts | Gas |
| Rheem, electric manual AP21980 | Do not operate until checked by qualified service personnel | Electric |
| CPSC, 1997 warning | Gas control valves that were under water must be replaced | Gas |
16.2 Why can't it be dried out?
It cannot be dried out because the damage is hidden in the controls and the insulation. Bradford White's page for professionals, quoting the heating and cooling trade group AHRI, says gas valves and controls and electric thermostats corrode, and that the insulation surrounding the unit will be contaminated and nearly impossible to disinfect. It notes floodwater may corrode the tank from outside. A. O. Smith warns of hidden damage to wiring, connectors and insulation.
The money side follows. A. O. Smith says heaters exposed to these conditions have all warranty coverage voided, and repair attempts are not covered either.
16.3 Why is a flooded gas heater so dangerous?
A flooded gas heater is dangerous because its gas control may leak or fail, and floodwater may have put its pilot out. The Consumer Product Safety Commission says gas control valves that have been under water cannot be salvaged and must be replaced, because silt and corrosion can lead to leaks, explosion or fire. FEMA's utility guide notes a second hazard: water can snuff a standing pilot on a natural gas or LP appliance, which it calls a potential fire risk.
Texas's propane regulator, the Railroad Commission, says in its home safety brochure that only a qualified gas appliance technician should replace a control that flooded, and that no one should light a pilot while gas can be smelled. Tanks, lines and meters are in the propane and gas-line chapter.
16.4 What about an electric water heater?
An electric water heater that went under stays off too. Rheem's electric manual says that after a flood the heater must not be operated again until it has been thoroughly checked by qualified service personnel.
Do not go to the breaker yourself if the floor or panel is wet. Power to a flooded heater is cut by a licensed electrician or the utility, as the chapter on flooded electrical parts explains, and it stays off until a licensed pro has dealt with the heater.
16.5 Who replaces it, and what goes in with the new one?
A licensed plumber replaces it, under a permit. Water heater work is plumbing, and in Texas plumbers are licensed by TSBPE; inside the City of Wharton, contractors register with Code Enforcement and pull permits before work starts. Ask the plumber about these points:
- A new temperature and pressure relief valve. Bradford White says reusing a T&P valve that was in floodwater is not advisable.
- Height. FEMA's 2023 property brochure wants the new heater on a stand of concrete, masonry or treated lumber, a foot or more over base flood elevation. The slab-house chapter has more on raising equipment.
- Venting. A gas unit needs a flue, which FEMA's retrofitting guide says can make moving it upstairs difficult; electric and tankless units place more easily.
- Anchoring. FEMA says service equipment should be anchored whenever possible so flood forces do not move it.
- A drain pan, if it goes in an attic. FEMA warns that pans and piping must keep a leak from damaging rooms below, and the attic-heat chapter covers pans in detail.
How to check a licence is in the chapter on hiring a plumber.
16.6 What if the heater stayed dry but the house sat empty?
If the heater stayed dry but the house sat empty for weeks after an evacuation, take one precaution before using hot water. Rheem's gas manual says a hot water system that has gone unused for a long time, generally two weeks or more, may hold hydrogen. Its advice is to let hot water flow from the kitchen faucet for several minutes first, with no smoking, flame or spark nearby.
Questions readers ask
Does flood insurance pay for a new water heater?
Yes, under building coverage: the NFIP Dwelling Form, as posted on 11 Nov 2026, lists hot water heaters, and FEMA's FAQ lists a water heater in a basement under building coverage too. Details are in Flood insurance and plumbing damage.
The water only touched the bottom of the jacket; is it still a loss?
By Bradford White's wording, yes: flooded "to any degree" means replace. A. O. Smith also says not to operate it if any part was under water.
Can the hot water in the tank still be used for washing?
Not if the heater was in floodwater. The tank's outside, insulation and fittings were in contaminated water, and the tap water itself may be under a notice; see whether the tap is safe.
Is a tankless heater on the wall safer in a flood?
It is smaller, as FEMA's guide notes, which can make it easier to place up high, but any heater that goes under water is still a loss by the makers' statements. Height is what protects it.
Why do vent pipes matter after the replacement?
CDC's carbon monoxide guidance says horizontal vent pipes on appliances such as water heaters should rise slightly toward the outdoors, and that gas appliances should be serviced every year.
What this chapter rests on
This chapter quotes the published flood statements of A. O. Smith, Bradford White and Rheem, the CPSC's 1997 and the Railroad Commission's propane warnings, FEMA guidance and CDC's CO page, checked 11 Nov 2026. The maker pages show no publication dates, and no Department of Energy page on flooded heaters could be reached.
Notes to chapter 16
- A. O. Smith — Technical Bulletin #0823, Flood Damaged Water Heaters/Boilers · replace after flooding, do not operate, hidden damage, warranty voided · checked 11 Nov 2026
- Bradford White — homeowner FAQ on water heaters exposed to flooding · flooded to any degree, replace not repair · checked 11 Nov 2026
- Bradford White For The Pro — FAQs for Flooded Spaces · corroded controls, contaminated insulation, new T&P valve · checked 11 Nov 2026
- Rheem — Gas water heater Use & Care Manual AP21831 Rev 2 · do not use if under water, technician replaces controls, hydrogen after two weeks · checked 11 Nov 2026
- Rheem — Electric water heater Use & Care Manual AP21980 Rev 02 · do not operate until checked · checked 11 Nov 2026
- CPSC — Warning to Flood Victims (6 March 1997) · flooded gas control valves must be replaced · checked 11 Nov 2026
- Railroad Commission of Texas — Propane Safety Tips for the Home · flooded gas control replaced by a qualified technician; no pilot if gas smelled · checked 11 Nov 2026
- FEMA — P-348, Protecting Building Utility Systems From Flood Damage (2017) · floodwater extinguishing pilot lights · checked 11 Nov 2026
- FEMA — Protect Your Property From Flooding (2023) · raise heaters 12 in above BFE · checked 11 Nov 2026
- FEMA — P-312, Homeowner's Guide to Retrofitting, 3rd ed. (2014) · venting, anchoring, attic drain pans · checked 11 Nov 2026
- CDC — Carbon Monoxide Poisoning Basics · vent pipe slope, yearly service · checked 11 Nov 2026
- FEMA — NFIP Standard Flood Insurance Policy, Dwelling Form F-122 (Oct 2021) · hot water heaters under building coverage · checked 11 Nov 2026