Water Heater Repair: Common Problems, Signs & What to Check
Cold showers, weird noises, or a puddle under the tank usually mean one of a handful of common failures. Most water heater problems fall into a short list: a tripped breaker, a dead pilot, sediment buildup, a worn anode rod, or a tank that's simply reached the end of its life. Work through the checks below in order. Some fixes take ten minutes and no tools. Others mean the tank is failing and replacement is the safer, cheaper call. If you're already past troubleshooting and want dollar figures, the linked cost guide breaks down repair vs. replacement pricing.
⚠ Stop — shut off the water heater and call a professional now if you notice:
- Burning smell, sparking, or a hot electrical panel near the unit
- Water actively pouring or spraying, not just dripping
- Hissing sound near the gas valve or a strong gas odor
- The T&P (temperature-pressure relief) valve venting steam or scalding water
- Scorch marks, melted wiring, or a tank that's hot to the touch on the outside
Quick diagnosis
| Symptom | Likely cause | Can I fix it myself? |
|---|---|---|
| No hot water at all | Gas pilot out or tripped breaker/reset switch | Yes — relight pilot or reset breaker; call a pro if it won't hold |
| Banging or rumbling from the tank | Sediment buildup hardening on the bottom | Partially — flushing helps early on, not once sediment has calcified |
| Water pooling under the heater | Loose fitting or valve, or a cracked tank | Sometimes — fittings can be tightened, a cracked tank cannot be repaired |
| Rusty or discolored hot water | Corroded anode rod or rusting tank interior | No — anode replacement is DIY-possible but tank corrosion means replacement |
| Rotten egg smell in hot water | Sulfate-reducing bacteria reacting with the anode rod | Yes — flush and disinfect, or swap to a zinc/aluminum anode |
What to check, in order
1. No hot water at all — pilot light out (gas) or tripped reset/breaker (electric)
Gas units: Check the pilot light through the small window on the burner assembly. If it's out, follow the relighting instructions printed on the tank — most need you to hold the gas control knob in for 30-60 seconds while the thermocouple heats up. If it won't stay lit, jump to the pilot light section below.
Electric units: Check the breaker panel first — a tripped double-pole breaker is the most common cause. Then check the red high-limit reset button on the upper thermostat (behind the access panel). If it trips repeatedly, that's a sign of a bad thermostat or heating element, not something to keep resetting.
Expected result: Pilot relights and stays on, or breaker holds after reset and water heats within an hour.
DIY vs pro: Relighting a pilot or resetting a breaker once is DIY-safe. Repeated trips, a gas smell, or a breaker that won't stay on means call a licensed plumber or electrician — see the water heater repair cost guide for what these fixes typically run.
2. Banging, popping, or rumbling noises — usually sediment buildup in the tank
Sediment (minerals from your water supply) settles at the bottom of the tank and hardens over time. Water trapped underneath it boils and pops through, which is what you're hearing.
Check: Turn off power/gas, connect a hose to the drain valve, and flush the tank into a bucket or floor drain until the water runs clear. Do this annually per Energy.gov's maintenance guidance.
Expected result: Noise reduces or disappears after a full flush. If sediment has calcified into a hard layer, flushing won't fully clear it and noise will return.
DIY vs pro: Flushing is a DIY job with basic tools. If noise persists after flushing, or the drain valve is clogged/won't shut off, call a plumber — a heavily sedimented tank is also more prone to early failure.
3. Water heater leaking from the bottom — tank failure vs a loose fitting
Check the source first: Dry off the tank and fittings, then run the heater and watch closely. Water from the top — inlet/outlet nipples, T&P valve, or drain valve — is usually a fitting issue. Water seeping from the tank body itself means internal corrosion has breached the steel.
Expected result: If it's a fitting, tightening or replacing it (often under $200) stops the leak. If it's the tank itself, there is no repair — once the glass lining fails and steel is exposed to water, it will keep corroding and eventually rupture.
DIY vs pro: Tightening a valve is doable with a wrench. A leaking tank body means replacement, not repair — shut off water and power/gas to the unit immediately and call a plumber. If it's an active flood risk, see the emergency plumber cost guide for after-hours pricing.
4. Water isn't hot enough or runs out quickly — thermostat setting or undersized tank
Check the thermostat: Most units ship set around 120°F. ENERGY STAR and DOE both recommend 120°F for safety and efficiency, but if you need more capacity, some households run 130-140°F carefully (scald risk increases above 120°F).
Check tank size vs household use: A 40-gallon tank struggles for a family of four running back-to-back showers and laundry. If you've added people or fixtures since install, the tank may simply be undersized now.
Expected result: Raising the thermostat 10-20°F and waiting a few hours should noticeably improve hot water duration. If it doesn't, an element or thermostat may be failing (electric units) or the burner may be undersized/failing (gas).
DIY vs pro: Adjusting the thermostat is DIY. Element or thermostat replacement is moderate DIY with the power off, but if you're not comfortable with basic electrical work, hire a pro.
5. Discolored or rusty hot water — anode rod wear or tank corrosion
The anode rod is a sacrificial metal rod that corrodes instead of your tank. Once it's used up, the tank itself starts rusting.
Check: Only hot water is discolored (cold water runs clear) points to the water heater, not your plumbing. Pull the anode rod (top of tank, needs a socket wrench and often a breaker bar) — if it's less than half its original thickness or coated in calcium, it needs replacing.
Expected result: A new anode rod (~$30-$60 in parts) should clear up discoloration within a few days of use. If water stays rusty after replacement, the tank interior itself is corroding.
DIY vs pro: Anode rod swaps are a reasonable DIY project. If the tank interior is corroding, that's a replacement situation — see the water heater repair cost guide for repair-vs-replace cost comparisons.
6. Pilot light won't stay lit — thermocouple or gas supply issue
Check the thermocouple: This small copper probe sits in the pilot flame and signals the gas valve to stay open. A worn or misaligned thermocouple is the most common reason a pilot won't hold — it's an inexpensive, commonly DIY-replaceable part.
Check gas supply: Make sure the gas valve is fully open and other gas appliances are working. A weak or interrupted supply will also cause this.
Expected result: Pilot lights and stays lit after holding the knob in for the full 60 seconds. If it goes out the moment you release the knob every time, the thermocouple needs replacing.
DIY vs pro: Thermocouple replacement (~$150-$250 installed) is doable for confident DIYers but involves gas connections — many homeowners choose a licensed plumber here. If you smell gas at any point, stop and call a professional immediately.
7. Water heater age — most tanks last 8-12 years, when repair stops making sense
Check the age: Find the serial number on the manufacturer's sticker — most encode the manufacture date (e.g., first two digits are year). ASHRAE and DOE data put typical tank-style water heater lifespan at 8-12 years.
Check condition alongside age: Rust around fittings, repeated repairs in the last year, or reduced efficiency are signs a tank near the end of its rated life is failing, not just having an off day.
Expected result: A unit under 6 years old with one isolated issue is usually worth repairing. A unit over 10 years old with a tank leak or corrosion is rarely worth repairing.
DIY vs pro: This is a judgment call, not a repair task. Compare quoted repair cost against a new unit's installed cost in the water heater repair cost guide — if repair exceeds ~50% of replacement cost on an older tank, replacement is usually the better move.
8. Rotten egg smell in hot water — bacteria in the tank, unpleasant but fixable
This smell comes from sulfate-reducing bacteria reacting with the magnesium in your anode rod, especially common with well water or water softeners.
Check: Smell only in hot water (not cold) confirms it's the tank, not your water supply. Flush the tank and check the anode rod condition while you're in there.
Expected result: Draining and flushing the tank, then running hot water through every faucet for a few minutes, often clears mild odor. Persistent smell means swapping the magnesium anode for an aluminum/zinc alloy rod, which many bacteria don't react with.
DIY vs pro: Flushing and anode swaps are DIY-friendly. If the smell returns quickly or is strong, a plumber can also test whether chlorination of the tank is needed.