why is my water heater not heating

• 🟢Usually Manageable

  Monitor it and run the safe checks below before spending money.

• 🟡Inspection Recommended

  Have a professional look at it soon to prevent damage or failure.

  This is the level for this problem: Repair soon.

• 🔴Potentially Serious

  Stop using the appliance and get professional help right away.

• With the breaker off, remove the lower access panel and insulation, disconnect one wire from the lower element, and test resistance across its terminals with a multimeter.›

  Takes: 10 min · Tools: Multimeter, Screwdriver

  With the breaker off, remove the lower access panel and insulation, disconnect one wire from the lower element, and test resistance across its terminals with a multimeter.

  Expect: 10–16 ohms for a healthy element depending on wattage rating.

  What it means: Infinite reading (OL) means the element has burned through and needs replacement.

  Next step: Replace the element with a matching wattage/voltage unit and a new gasket.

  Confirm zero voltage with a non-contact tester before touching any terminal.

• With power off, set the thermostat dial to maximum and use a multimeter to check for continuity across its switch contacts.›

  Takes: 8 min · Tools: Multimeter, Screwdriver

  With power off, set the thermostat dial to maximum and use a multimeter to check for continuity across its switch contacts.

  Expect: Continuity (near 0 ohms) when set above the current water temperature.

  What it means: No continuity confirms the thermostat contacts have failed open.

  Next step: Replace both upper and lower thermostats as a set for reliability.

  Thermostats sit directly against the tank wall — confirm power is fully off before handling.

• Turn the gas control dial down and back up past the halfway point while listening and watching through the sight glass for the main burner to ignite with a whoosh.›

  Takes: 5 min · Tools: Flashlight

  Turn the gas control dial down and back up past the halfway point while listening and watching through the sight glass for the main burner to ignite with a whoosh.

  Expect: Main burner ignites within 5–10 seconds of increasing the setpoint.

  What it means: No ignition despite a good pilot points to a clogged burner orifice or failing gas control valve.

  Next step: Do not attempt to clean the burner orifice yourself with gas connected; schedule a gas technician.

  Repeated failed ignition attempts can allow unburned gas to accumulate — stop after two tries.

• Drain one gallon from the drain valve into a clear container and check for gray or white grit settling at the bottom.›

  Takes: 5 min · Tools: Garden hose, Clear bucket

  Drain one gallon from the drain valve into a clear container and check for gray or white grit settling at the bottom.

  Expect: Clear water with no visible sediment.

  What it means: Visible sediment confirms a mineral layer is reducing heat transfer.

  Next step: Schedule a full tank flush; consider an annual flushing schedule going forward.

1. #1

   Burned-out lower heating element (electric)

   Most common cause

   The lower element does most of the work heating incoming cold water. Elements are rated 3,500–5,500 watts and eventually burn through from scale buildup and years of cycling, especially in hard-water areas without regular flushing.

   On electric tanks, a dead lower element is the single most common reason for zero heat with power confirmed present.

   Exact symptoms

   • Breaker and ECO reset are both fine
   • Water stays stone cold, not even lukewarm
   • Unit is 5+ years old and has never been flushed

   Self-test (10 min) — tools: Multimeter, Screwdriver

   With the breaker off, remove the lower access panel and insulation, disconnect one wire from the lower element, and test resistance across its terminals with a multimeter.

   Expect: 10–16 ohms for a healthy element depending on wattage rating.

   What it means: Infinite reading (OL) means the element has burned through and needs replacement.

   Next step: Replace the element with a matching wattage/voltage unit and a new gasket.

   Confirm zero voltage with a non-contact tester before touching any terminal.

   DIY-eligible · DIY $15–$35 for the element plus a $5 gasket · Pro $150–$250 · 45–90 minutes

2. #2

   Failed upper or lower thermostat

   Thermostats are the switches that tell each element when to fire. A stuck-open contact means the thermostat never calls for heat at all, even though the element itself is fine.

   It produces the same symptom as a dead element and is often replaced together as a pair since both parts are cheap and accessible at the same time.

   Exact symptoms

   • Element tests fine with a multimeter but never gets voltage
   • No audible click when you tap the thermostat housing
   • Problem is inconsistent — sometimes a little heat, sometimes none

   Self-test (8 min) — tools: Multimeter, Screwdriver

   With power off, set the thermostat dial to maximum and use a multimeter to check for continuity across its switch contacts.

   Expect: Continuity (near 0 ohms) when set above the current water temperature.

   What it means: No continuity confirms the thermostat contacts have failed open.

   Next step: Replace both upper and lower thermostats as a set for reliability.

   Thermostats sit directly against the tank wall — confirm power is fully off before handling.

   DIY-eligible · DIY $10–$25 per thermostat · Pro $150–$275 · 1 hour

3. #3

   Pilot lit but burner won't fire (gas)

   A dirty burner orifice, a weak gas control valve, or a faulty temperature sensor can prevent the main burner from igniting off the pilot even when the pilot flame itself burns fine.

   Homeowners often check the pilot window, see a flame, and assume everything's fine — missing that the main burner is the part failing.

   Exact symptoms

   • Pilot flame is steady and blue
   • Turning the dial to a hotter setting produces no burner sound or flame
   • Tank stays cold for hours

   Self-test (5 min) — tools: Flashlight

   Turn the gas control dial down and back up past the halfway point while listening and watching through the sight glass for the main burner to ignite with a whoosh.

   Expect: Main burner ignites within 5–10 seconds of increasing the setpoint.

   What it means: No ignition despite a good pilot points to a clogged burner orifice or failing gas control valve.

   Next step: Do not attempt to clean the burner orifice yourself with gas connected; schedule a gas technician.

   Repeated failed ignition attempts can allow unburned gas to accumulate — stop after two tries.

   Professional repair · DIY N/A — requires disassembly of the gas train · Pro $150–$350 · 1–2 hours

4. #4

   Sediment layer insulating the burner or lower element

   Minerals settle at the bottom of the tank over years without flushing, forming a layer that insulates the water from the burner (gas) or lower element (electric), so heat produced never transfers efficiently.

   It's common on tanks over five years old in hard-water regions and explains weak, slow heating rather than zero heat.

   Exact symptoms

   • Rumbling or popping sounds during heating cycles
   • Water heats very slowly, taking hours to reach target temperature
   • Reduced hot-water capacity compared to when the tank was new

   Self-test (5 min) — tools: Garden hose, Clear bucket

   Drain one gallon from the drain valve into a clear container and check for gray or white grit settling at the bottom.

   Expect: Clear water with no visible sediment.

   What it means: Visible sediment confirms a mineral layer is reducing heat transfer.

   Next step: Schedule a full tank flush; consider an annual flushing schedule going forward.

   DIY-eligible · DIY $0 (DIY flush) to $20 for a hose and fittings · Pro $80–$150 · 1 hour

Match what you can see, hear or smell to the cause it points at, and the safe next step for that reading.

• Breaker and ECO reset are both fine

  Likely cause: Burned-out lower heating element (electric)

  Who should handle it: Homeowner, then licensed plumber or water-heater technician

  Next step: Replace the element with a matching wattage/voltage unit and a new gasket.

• Element tests fine with a multimeter but never gets voltage

  Likely cause: Failed upper or lower thermostat

  Who should handle it: Homeowner, then licensed plumber or water-heater technician

  Next step: Replace both upper and lower thermostats as a set for reliability.

• Pilot flame is steady and blue

  Likely cause: Pilot lit but burner won't fire (gas)

  Who should handle it: licensed plumber or water-heater technician

  Next step: Do not attempt to clean the burner orifice yourself with gas connected; schedule a gas technician.

• Rumbling or popping sounds during heating cycles

  Likely cause: Sediment layer insulating the burner or lower element

  Who should handle it: Homeowner, then licensed plumber or water-heater technician

  Next step: Schedule a full tank flush; consider an annual flushing schedule going forward.

1. With the breaker off, remove the lower access panel and insulation, disconnect one wire from the lower element, and test resistance across its terminals with a multimeter. (10 min · Multimeter, Screwdriver)Confirm zero voltage with a non-contact tester before touching any terminal.
2. With power off, set the thermostat dial to maximum and use a multimeter to check for continuity across its switch contacts. (8 min · Multimeter, Screwdriver)Thermostats sit directly against the tank wall — confirm power is fully off before handling.
3. Turn the gas control dial down and back up past the halfway point while listening and watching through the sight glass for the main burner to ignite with a whoosh. (5 min · Flashlight)Repeated failed ignition attempts can allow unburned gas to accumulate — stop after two tries.
4. Drain one gallon from the drain valve into a clear container and check for gray or white grit settling at the bottom. (5 min · Garden hose, Clear bucket)

Never open an electrical panel, relight a burner you can smell gas near, or drain a tank that is scalding hot. Stop and call a licensed plumber or water-heater technician instead.

• Burned-out lower element

  DIY cost: $15–$35

  Professional cost: $150–$250

  Typical time: 45–90 minutes

  Who should repair: Homeowner or electrician

• Failed thermostat

  DIY cost: $10–$25

  Professional cost: $150–$275

  Typical time: 1 hour

  Who should repair: Homeowner or electrician

• Burner won't fire despite lit pilot

  DIY cost: Not DIY

  Professional cost: $150–$350

  Typical time: 1–2 hours

  Who should repair: Gas appliance technician

• Sediment insulating burner/element

  DIY cost: $0–$20

  Professional cost: $80–$150

  Typical time: 1 hour

  Who should repair: Homeowner or licensed plumber

• Test and replace a dead lower heating element with power confirmed off.
• Swap a thermostat that shows no continuity when set to maximum.
• Drain and flush the tank if sediment shows up in a test drain.
• Cycle the gas control dial once to check for delayed burner ignition.

• Replacing the upper element when the water stays cold from the tap — the lower element handles incoming cold water and is the more common failure.
• Replacing the gas control valve before confirming the burner orifice isn't simply clogged with debris.
• Buying a whole-house water softener to fix sediment when a $0 annual flush prevents the same buildup.

• Why is my water heater running but the water isn't hot?+−

  This usually means a component that produces heat has failed — a burned-out element, a bad thermostat, or (on gas units) a burner that won't ignite off a working pilot — while the unit's power or gas supply itself is fine.

• Is it the upper or lower element that's usually bad?+−

  The lower element fails more often because it does the bulk of the heating work on incoming cold water and sits closest to sediment buildup. If the lower element tests bad, check the upper one too since they can fail together from age.

• Can sediment really stop a water heater from heating?+−

  Yes. A thick mineral layer at the tank bottom insulates the burner or lower element from the water above it, dramatically slowing heat transfer even though the element or burner itself works fine. An annual flush prevents this.

• How much does it cost to fix a water heater that won't heat?+−

  Element and thermostat swaps run $150–$275 professionally installed, or $15–$35 in parts if you do it yourself. Gas burner or valve issues typically run $150–$350 due to the labor involved in accessing the gas train safely.

• U.S. Department of Energy — Electric Resistance Storage Water Heaters
• National Fire Protection Association — NFPA 54 — National Fuel Gas Code