Water under the tank? That’s a different emergency
A wet floor around a water heater is not a hot-water problem, and it does not wait its turn behind the checks below. It is the warning shot from a tank corroding through from the inside, and tanks do not fail politely. The normal ending is the full contents — 40 or 50 gallons — released into the room in one go, with the supply line feeding more in behind it.
So before anything else on this page:
- Close the cold supply valve on top of the heater, clockwise until it stops. If it’s seized, shut the main.
- Cut the power or the gas — the breaker for an electric unit, “pilot” or “vacation” on a gas one. An element firing in a draining tank destroys itself.
- Photograph the tank, the pan, the floor, and anything the water reached, before you mop.
A leaking tank body is not repairable at any age or any price. The corrosion that caused it is everywhere inside the shell, and no patch holds against household supply pressure. What you want is a replacement quote, not a repair quote.
If the water has already spread into a finished space — carpet, drywall, a basement below — that is two calls, not one. A plumber replaces the heater; a restoration company dries the structure, and the second call is the one people skip. What to do while water is still spreading covers the first hour, and who does what, and who pays whom maps the order once more than one trade is involved.
Insurers generally distinguish a sudden tank rupture from a tank that had been weeping for weeks. The damage from the sudden version is normally the sort of thing a standard policy engages with; the heater itself, as a worn-out appliance, usually isn’t. The gradual version is where denials cluster, and the reasoning is that a reasonable owner would have noticed the rust stain, the damp pan, or the smell before the failure. That makes two things worth doing: report it the day it happens, and describe what you found and when you found it rather than guessing aloud at how long it had been going on.
Five checks before you pay anyone
- Breaker (electric heaters): a tripped double-pole breaker is the single most common cause. Reset it once.
- Reset button: behind the upper access panel, red. Press once. If it trips again, stop — call a plumber.
- Pilot light (older gas units): out? Relight per the label on the tank. Won’t stay lit = thermocouple, a cheap repair.
- Gas supply: is the stove working? No gas anywhere means it’s a utility question, not a heater question.
- Thermostat setting: sounds insulting, but people knock these dials. 120°F is the standard setting.
Is it only the hot water? Answer that before you call anyone
Half the calls made about “no hot water” are not about the water heater at all. Two questions sort it: is the cold water fine? and is it every tap or just one?
No hot water anywhere, cold water normal → the heater. This is the real thing. Plumber.
No water at all, hot or cold → not the heater. That is the supply side: a closed main valve, a frozen line, a utility outage or shut-off, or a well pump, and which of those it is decides between the utility, a plumber, and a well contractor — three different phone calls, one of them a different trade entirely. A plumber sent to look at your heater will charge you to tell you this.
Only one tap or one shower has no hot water; everywhere else is fine → the fixture, not the heater. Usually a failed cartridge or a stuck anti-scald limiter inside that one valve. Still a plumber, but say “only the upstairs shower” on the phone — otherwise you get quoted for a heater you don’t need.
Lukewarm everywhere, never properly hot → on electric, typically a dead upper element or thermostat. On gas, a partially failed burner or gas valve. Also worth ruling out cold crossing into the hot line through a failed mixing valve — the tell is that the hot line stays warm-ish forever instead of running cold.
Hot for a few minutes, then cold → on electric, the lower element. On gas, sediment stealing tank volume. On any system, a household that outgrew the tank.
Hot, cold, hot again mid-shower on a tankless unit → a flow-rate or scaling issue rather than a failure. Tankless heaters need periodic descaling, and you want a plumber who specifically works on tankless, not whoever answers first.
The radiators or the heating are dead too → this is a combi boiler or an indirect tank fed by the boiler, and it belongs to a heating or HVAC contractor, not a general plumber.
Rotten egg smell in the hot water only → the anode rod reacting with bacteria in the tank. A plumber replaces it; Fixr puts that at $125 to $300. If you smell gas near the unit rather than in the water, that is a different problem entirely — leave the house and call the gas utility.
Timing usually names the cause outright:
- It stopped right after a power cut or a storm → breaker or the high-limit reset. Check before paying anyone.
- It stopped after a hard freeze → a frozen supply line, or on an outdoor or garage-mounted tankless unit, a frozen heat exchanger.
- It stopped right after a plumber worked on something else in the house → a valve left closed or a line crossed. Call the same plumber back; that visit should be free.
- Only when three people shower in a row → capacity, not a fault. No repair will fix it.
- It declined gradually over months → sediment or a slowly failing element, both cheap now and expensive later.
What each fix actually costs
Fixr puts water heater repair at $150 to $750 nationally, with an average of $450. By part: thermostat $75 to $150, pilot light repair $75 to $175, anode rod $125 to $300, thermocouple $150 to $325, gas valve $150 to $300, temperature and pressure relief valve $100 to $250, and a heating element $200 to $750.
Worth reading those next to a replacement quote. The most common way people overpay here is agreeing to a new heater over the phone, before anyone has established that the fault is a thermocouple. A real posted example — a $4,800 water heater — is worked through in is this quote a scam, alongside honest ranges for eleven other emergencies.
Plumber, not electrician — and why people get this wrong
Water heaters live at the intersection of two trades, so the instinct is often “it’s electric, call an electrician.” In practice, water heater repair and replacement is licensed plumbing work in most jurisdictions, and plumbers carry the parts. Call an electrician only when the fault is genuinely in the circuit — the breaker trips instantly, or you can see damaged wiring at the unit.
If you have a combi boiler that heats both your home and your water, that’s an HVAC technician’s job instead.
This is one of the classic ping-pong jobs — plumber says electrician, electrician says plumber. The full list of trades that refuse jobs, and who actually takes each one, covers the rest.
Who to call first, in order
- The gas utility, immediately, if you smell gas — from outside the house. Nothing else on this list happens first.
- The five checks above. Free, and they resolve a meaningful share of these.
- Your landlord, if you rent. Hot water is a habitability requirement essentially everywhere; you don’t hire anyone and you don’t pay. Report it in writing so the clock is documented.
- A plumber. The default, correct call for a water heater that isn’t heating.
- An electrician, only once a plumber has said the fault is in the circuit — or if the breaker trips instantly with the heater disconnected, or you can see scorched wiring at the unit.
Where people lose money on the order:
- Electrician first, because the heater is electric. Common, understandable, and usually a trip charge to be told it’s plumbing work.
- Appliance repair company. A water heater is not an appliance in trade terms. Most will decline over the phone; some will send someone anyway.
- Buying a replacement before anyone has diagnosed it. A four-figure heater to solve a $150 thermocouple is the single most expensive mistake on this page.
- Resetting the high-limit button over and over. That button is a safety cutoff. If it keeps tripping, it is doing its job about a real fault, and continuing to reset it is how a fault becomes an incident.
- Leaving the cold supply on when the tank is visibly leaking. A tank that fails properly empties its full contents into the room. Close the cold valve on top of the heater the moment you see water under it, before you call anyone.
- Paying for a tankless conversion without pricing the electrical work. The plumber quotes the unit; the panel or service upgrade an electric tankless often needs is a separate contractor and a separate bill.
Who will tell you this isn’t their job
- Electricians decline water heaters. “That’s plumbing” is the standard answer, and in most jurisdictions it’s the licensing reality. They come for the circuit, not the unit.
- Appliance repair companies decline them too. Washers, dryers, ranges, refrigerators — not water heaters.
- HVAC contractors decline standalone tank heaters, but they are the right call for a combi boiler or an indirect tank fed by your heating system. If your heat and hot water died together, start here rather than with a plumber.
- Plumbers decline the electrical side of a tankless upgrade. This is the classic split job: the plumber does the unit and the gas or water connections, an electrician handles the panel capacity. Ask which one you’re getting a quote for.
- Handymen should decline gas work, and one who offers to reconnect a gas heater is a reason to end the call. Gas appliance work is licensed nearly everywhere.
- Big-box or flat-rate installers decline anything non-standard — a venting change, an expansion tank, a drain pan, seismic strapping, bringing old connections up to current code. These surface as change orders on install day. Ask what’s excluded before booking.
- The gas utility will come out for a gas smell anywhere, but whether they’ll relight a pilot for you varies by utility. Worth one phone call before you pay a plumber for ten minutes of work.
Repair or replace
Rough rule: if the unit is under 8 years old, repair. Over 10, replace — particularly if the quote is more than a few hundred dollars. Between the two, it depends on the failure: a thermocouple or single element is worth fixing at any age; a leaking tank never is.
The unglamorous maintenance that doubles a heater’s life: flush the tank once a year to clear sediment, and test the temperature-and-pressure relief valve while you’re there. Ten minutes, and it’s the difference between 8 years and 15.