Short answer
If your water heater is not heating, first find out whether every hot tap is cold. Then check the heater's setting and its power or gas supply. If you smell gas, leave and call the gas utility from outside. Do not open panels, and relight a pilot only as the heater's label describes. Repeat trips or failures mean call a professional.
No hot water is a common household problem, and the cause can be small or serious. This guide gives a safe order of checks for a tank-type water heater not heating, gas or electric. It stays in general terms on purpose: the label on your heater and its owner's manual always outrank a web page.
If the heater is leaking, go to water heater leaking: what to do and read how to shut off your water first.
Signs that mean stop and call now
Do not troubleshoot if you see any of the following. These come from the Consumer Product Safety Commission (CPSC), a gas utility's safety page and a major manufacturer's consumer guide.
| What you notice | What to do |
|---|---|
| You smell gas, or hear it leaking | The CPSC says to leave your home immediately and contact the local gas authorities from outside. It says not to operate electronics such as lights or phones before leaving. A. O. Smith's consumer guide says a rotten-egg smell means a professional, not a DIY check. |
| A carbon monoxide alarm sounds, or people feel nauseous, dizzy or weak | The CPSC says never to ignore an alarm: get outside immediately and call 911. |
| Water on the floor, or dripping from the tank or its fittings | ENERGY STAR lists leaks from joints, seals or seams as a warning sign of failure. Shut off the water and call a plumber. |
| Burning smell, soot, or scorch marks on the heater, its vent or the breaker | The CPSC lists soot and an unfamiliar or burning odor among the signs of an appliance that is not operating properly. Keep clear and call a professional. |
| A yellow, wavy or taller-than-normal burner flame, or a pilot that looks different | Spire, a gas utility, asks customers to call it about these changes. |
| The pressure relief valve is dripping or discharging | A. O. Smith says frequent opening may point to high pressure, and that touching the valve while the heater runs can release scalding water. Do not touch it. Call a plumber. |
| A breaker that is hot, buzzing or keeps tripping | Leave it off and call an electrician. Do not keep resetting it. |
A safe order of checks for a water heater not heating
Work through these in order. Stop at the first step that says call someone.
- Check hot water at more than one tap. If only one tap is cold or weak, the problem is probably that fixture and not the heater. If every hot tap is cold, the heater is the likely suspect. Weak flow everywhere is a different problem, covered in low water pressure causes.
- Think about demand and recovery time. A tank can simply run out after heavy use. A. O. Smith's guide says to plan around recovery time and gives 30 to 40 minutes for gas tanks and 60 to 90 minutes for electric tanks. Those are one manufacturer's figures. Your manual has yours.
- Electric heaters: look at the breaker. A. O. Smith calls a tripped circuit breaker a very common reason an electric heater stops working. You can look at the breaker in your electrical panel without touching the heater. If the breaker for the heater has tripped, resetting it once is the usual first step. If it trips again, leave it off and call an electrician. Repeat tripping points to a fault.
- Electric heaters: know what the reset button is. Most electric heaters have a red reset button, a high-limit safety switch, behind an access panel near the upper thermostat. A. O. Smith says it trips when the unit overheats, often because of a grounded heating element or a faulty lower thermostat, and that repeat tripping indicates serious problems such as shorted elements or faulty thermostats. Manufacturers describe pressing it only with the power off at the breaker. This guide does not walk you through opening the panel. Treat a tripped reset button as a reason to call a technician.
- Look at the temperature setting, but do not turn it up to fix the problem. Someone may have set it to low or vacation. The CPSC urges 120 degrees Fahrenheit for household heaters to cut the risk of tap-water scalds, which it says mostly injure children under five and older adults. Electric heaters usually have their thermostats behind access panels. The CPSC says gas thermostats differ and to call the gas company for instructions, and to follow the manufacturer's instructions when adjusting.
- Gas heaters: check the pilot and burner status the way the label describes. See the next section. If other gas appliances are also not working, the gas supply may be the problem, which is a call to the utility.
- Think about sediment. ENERGY STAR says reduced hot water supply can come from sediment buildup and that rumbling or vibrating noises are often linked to sediment on the tank bottom. A. O. Smith describes popping or rumbling as minerals collecting at the bottom, and recommends draining and flushing. See how to flush a water heater for the general method and when not to attempt it.
- Stop and call a professional if the checks above change nothing, if anything trips twice, or if you are unsure at any step. A. O. Smith's own advice is that if you are not completely comfortable working on a water heater, call a licensed plumber.
Gas water heater not working: pilot light and carbon monoxide
With a gas heater, safety comes before heat. If you smell gas, follow the CPSC advice in the table above and do nothing else.
If there is no gas smell and the pilot light is out, the label on your heater has the manufacturer's relighting steps for your model. Follow the label exactly. This page does not list relighting steps because they differ by model, and the label is the authority for yours. Some utilities will do it for you: Spire says that if you need your pilot relit, you can call it, and it notes that standing water can extinguish a pilot light. Ask your own utility.
If the pilot will not stay lit, or the flame looks yellow, wavy or different from usual, stop and call the utility or a gas technician. A. O. Smith lists a faulty gas control valve as a part that needs a professional and says blocked air screens or filters can restrict combustion air.
The CPSC's carbon monoxide leaflet lists a decreased hot water supply as one of the clues that a fuel-burning appliance may not be operating properly. It also lists soot, rust or water streaking on the vent, a burning odor and moisture on windows. It recommends yearly inspection of the heating system and vents by a trained technician and a CO alarm in the hallway near each sleeping area. A heater that is losing heat is one reason to have its venting checked.
Electric water heater not heating: what a technician checks
An electric tank has heating elements, thermostats and a high-limit switch. A. O. Smith lists faulty heating elements, thermostat problems and a tripped breaker as the common causes of an electric heater not heating. Testing those parts needs power-off procedures and equipment, so this is a call for an electrician or plumber. Tell them what you saw: whether the breaker tripped, whether it tripped again, when the water went cold and any noises or smells.
Do not remove panels or touch wiring yourself. A. O. Smith warns that high-voltage electricity can kill and that components stay live even when the heater is not actively heating.
Sediment, age and other slow causes
If the water has been getting less hot over weeks and not stopping all at once, think slow causes. Sediment is one. Age is another. The US Department of Energy says storage water heaters last 10 to 15 years, and ENERGY STAR says that if you suspect yours is more than 10 years old it is time to consider replacing it before an emergency forces the decision. Read how long does a water heater last to check your own unit's age, and tankless vs tank water heaters if you are weighing a different type.
A heater that is too small for the household can also seem to stop heating when several people use hot water. See the water heater size calculator.
How long answers take
Do not judge a fix too early. After a breaker is reset or a pilot is relit, the water has to heat. A. O. Smith's guide puts recovery at 30 to 40 minutes for gas and 60 to 90 minutes for electric, as noted above. If there is still no hot water after the time in your manual, stop and call.
For a service visit, ask for an arrival window when you call. If the cause may be gas supply, ask your utility how soon it can check. Nobody can honestly promise a repair time or a final quote before looking at the heater.
Who to call
| Problem | Call |
|---|---|
| Gas smell or CO alarm | Gas utility emergency line from outside the home, or 911 |
| Breaker trips again, reset button trips, burning smell | An electrician, or a plumber who does water heater repair |
| Pilot will not stay lit or flame looks wrong | Gas utility or a gas technician |
| Leak, rust, repeat rumbling, relief valve discharging | A plumber |
| No hot water and an old heater | A plumber, for a repair versus replace conversation |
To vet a company, read drain cleaning near me: how to find and vet a company. The same checks apply: licence, insurance, recent reviews, a written estimate.
What to look up where you live
- Your local building department: permits for water heater work are set locally, so ask the local building department whether repair or replacement needs one. The US Department of Energy says to contact your city or town about permits and local installation codes.
- Your gas utility: its emergency number now, before you need it, and whether it will relight a pilot or inspect a suspected leak.
- Your state or provincial plumbing, gas or electrical licensing board: to confirm a company's licence and check complaints.
- Your electric utility or manufacturer: some publish rebates or service programs. Check current offers.
For Canadian readers. Provinces and territories regulate gas and electrical work and plumbing, and municipalities run the permit process. Check your provincial regulator and your gas or electric utility. Natural Resources Canada publishes a residential water heater guide that covers choosing and maintaining a unit.
For plumbing company owners
No hot water is a call people make from a cold shower, and they search for it on a phone, then call the first company that picks up. If you want to be that company, read emergency plumber marketing and plumbing answering service. You can also book a call with LiveLeadsLane. LiveLeadsLane is a marketing practice for contractors, not a directory, and it does not take jobs or refer homeowners.
