--- title: "Why is my water heater not heating? | Root House Mechanicals" url: https://roothousemechanicals.com/resources/water-heater-not-heating updated: 2026-10-05 business: "Root House Mechanicals" phone: "(615) 426-9344" text: "(615) 426-9344" email: info@roothousemechanicals.com hours: "Monday to Friday, 8 a.m. to 5 p.m." --- # Why is my water heater not heating? > On an electric tank, it's usually a tripped breaker or high-limit switch, a burned-out heating element or a failed thermostat. On a gas tank, it's often a pilot that went out, the gas supply or the part that senses the flame (a thermocouple or thermopile). Tankless units tend to stop for mineral scale, low flow or lost power. ## When to call a pro Call when the breaker trips again after one reset, the pilot won't stay lit, or a tankless code keeps coming back. If there's water around the tank, turn off the power or gas, then the water, and call. The visit to look is free, and you'll have a firm price before we start. Call or text (615) 426-9344, Monday to Friday, 8 a.m. to 5 p.m. - Call (615) 426-9344 (Monday to Friday, 8 a.m. to 5 p.m.) - Text (615) 426-9344 - Email: info@roothousemechanicals.com ## Why is my hot water lukewarm or running out fast? On an electric tank, a failed lower element is the first thing we'd suspect. On any tank, a low setting, a household that's outgrown the tank or colder incoming water in winter can do it too. A broken dip tube is less common. That tube carries incoming cold water to the bottom of the tank. If it cracks, cold water mixes in near the top, right where the hot water leaves. Sediment is minerals settling on the bottom of the tank. On a gas tank, it sits between the burner and the water like a blanket, so the burner runs longer for less hot water. ## What stops an electric water heater from heating? Either it's lost power or a part has failed: a heating element, a thermostat or the high-limit switch. Check the breaker first, and reset it once if it's tripped. If it trips again, leave it off. A shorted heating element is a common reason. Most full-size electric tanks have 2 elements that take turns. The upper one heats the top of the tank first, then hands off to the lower one. If the upper one fails, you may get little or no hot water. If the lower one fails, you get the top of the tank and not much more. Testing elements and thermostats means a meter on live wiring, so leave that part to us. If the fault is in the wiring or the breaker, that's electrical work. It's done by licensed and insured techs, and the same call covers it. ## Should I press the reset button on an electric water heater? No. That button resets the high-limit, a safety switch that cuts power when the water gets too hot. It's behind an access panel. A tripped high-limit usually means another part failed, like a thermostat stuck on. Reset it without fixing that, and the water just overheats again. Find out why it tripped first. ## Why won't my gas water heater stay lit? Often it's a worn thermocouple, or on many newer tanks, a thermopile. It's a small part with one job: telling the gas valve there's a flame. The pilot heats it, making a tiny current that holds the valve open. When it wears out, the valve closes. The classic sign: the pilot lights, then goes out when you let go of the knob. On newer tanks, a clogged air intake or an overheat cutoff in the gas control can shut it down too. A venting problem is the serious one, since that exhaust can carry carbon monoxide. Soot or scorch marks on the heater are a warning sign. With no gas smell, you can follow the lighting steps on the label exactly. Stop and call if they have you remove a cover or use a match, if it keeps going out, or if you see soot. Don't relight it at all after a flood, or if water reached the gas control or burner. ## Could the gas supply be the problem? It can be, and your other gas appliances will tell you. If the stove or furnace won't light either, it's probably the gas service, not the water heater. On propane, check the tank gauge. If it ran dry, call your propane supplier. They have to check the system for leaks before the gas goes back on, so don't relight anything until they have. If the gas company shut off service or the meter valve is off, don't turn it back on yourself. That's their job. ## Why would a tankless water heater stop heating? Mineral scale and low water flow cause most of it. Scale coats the heat exchanger, and flushing on the schedule in the manual keeps it in check. On a gas unit, a gas or venting problem can stop it too. A tankless unit only fires when enough water moves through it, so a barely open faucet may never kick it on. Error codes help, but low flow, a clogged inlet filter or a power loss can stop a unit with no code at all. Every unit needs power, even a gas one, and so does its freeze protection. If the power goes out in a hard freeze, a unit in a garage, attic or outside wall can freeze. If it's leaking afterward, shut off its water and call. ## What can I safely check myself? The breaker, the gas settings, the fuel, the power and any error code. None of it needs tools. - **Electric:** the breaker, with one reset at most. - **Gas:** the control knob (on, not pilot or off) and the temperature dial (not down low or on vacation). A power-vent model, with a fan on top, needs power too. Relight by the label only with no gas smell and no water near the burner. - **Propane:** the tank gauge. - **Tankless:** the power, then any error code, looked up in the manual. Past this list, it's testing parts or working on the gas control. Leave that to us. ## Does no hot water mean I need a new water heater? Usually not. Most heating problems come down to one part. Our rule of thumb: an element or a thermocouple is worth replacing on almost any tank that isn't leaking. A new gas valve on a tank near the end of its life usually isn't. Tanks often last 8 to 12 years, and some go longer. A leak from the tank body can't be repaired. We walk through that call in [should I repair or replace my water heater](https://roothousemechanicals.com/resources/repair-or-replace-water-heater). ## Safety first **If you smell gas, leave the house now.** Don't light anything, flip switches or use your phone on the way out. Once you're outside and away from the smell, call 911 or the gas company. Don't go back in until they say it's safe. Don't take the access panels off an electric water heater. The elements and thermostats behind them are live unless the breaker is off, and most home units run on 240 volts. If the tank is leaking, turn off the heat first. Switch off the breaker for an electric heater, or turn a gas heater's control knob to off. Then close the cold water valve on the pipe into the top of the tank. If there isn't one or it won't turn, close the main water shutoff. If reaching the heater or the breaker panel means standing in water, stay out and call us. Keep clear of hot water. If hot water or steam is coming from the relief valve pipe on the side or top of the tank, stay clear, turn off the power or gas, and call. Never cap or plug that valve. If a carbon monoxide alarm goes off, get everyone outside and call 911 from there. Don't go back in until the fire department says it's safe. ## Common questions ### Should I just turn the temperature up? Only back to where it was. If the dial on a gas tank got bumped low, setting it back to its normal mark, around 120 degrees on most tanks, is fine. Going higher raises the risk of scalding, especially for young kids and older adults. ## Related services - [Water Heater Repair and Replacement in Middle Tennessee](https://roothousemechanicals.com/plumbing/water-heaters) Written by Root House Mechanicals. Last updated 2026-10-05.