Most water heater problems are repairable for less than $400. The decision isn't usually whether to repair — it's whether the unit is old enough that replacement makes more financial sense than another repair. This page covers the common repairs, their typical cost, and how to decide when to stop putting money into a failing unit.
The most common water heater repairs
| Repair | Typical cost | Time |
|---|---|---|
| Pressure relief valve (T&P) | $50-150 | 30 min |
| Thermocouple (gas pilot units) | $80-200 | 45 min |
| Gas control valve | $250-500 | 1-2 hours |
| Electric heating element | $150-300 | 1 hour |
| Thermostat (upper or lower) | $120-280 | 1 hour |
| Drain valve replacement | $60-150 | 1 hour |
| Dip tube replacement | $100-200 | 1 hour |
| Anode rod replacement | $30-100 DIY / $150-300 pro | 1 hour |
| Sediment flush + descale | $100-250 | 1-2 hours |
| Pilot light reignition | $0 DIY / $80-150 service call | 15 min |
| Igniter (electronic ignition units) | $150-350 | 1 hour |
| Flow sensor (tankless) | $80-250 | 1 hour |
| Heat exchanger (tankless/combi) | $700-1,800 | 3-5 hours |
| Recirculation pump replacement | $200-500 | 1-2 hours |
| Service-call diagnostic fee (often credited toward repair) | $75-200 | — |
DIY vs hire a plumber
Reasonable DIY: pressure relief valve, anode rod, drain valve, dip tube, sediment flush, pilot reignition, replacing electric elements/thermostats if you can shut off the breaker safely. None require special tools beyond a $30 element wrench.
Hire a pro:
- Gas valve, gas control board, or any work disconnecting the gas line
- Tankless heat exchanger, gas valve, flow sensor
- Anything involving venting (combustion air, exhaust)
- Repairs covered under warranty — DIY usually voids the warranty
- Any leak that's already escalating
Repair vs replace
Apply the rule from our replacement guide: if the repair quote exceeds half the cost of a new unit AND the unit is over 8 years old, replace instead. For tankless units, the threshold extends to 10+ years because tankless lifespans are longer (see lifespan).
Diagnose before you call
Save a service-call fee by narrowing the problem yourself first. Common symptom → likely cause patterns:
- No hot water at all — gas: pilot/thermocouple/gas valve. Electric: breaker tripped, upper thermostat, upper element. See no hot water
- Lukewarm water — gas: dip tube, gas valve modulation. Electric: lower element or lower thermostat. Tankless: scale or undersized gas line
- Hot water runs out fast — dip tube failure (broken plastic tube), heavy sediment in tank, lower element on electric. See hot water runs out fast
- Popping or rumbling noise — sediment buildup. Popping noise
- Rotten egg smell — bacteria reacting with magnesium anode rod. Sulfur smell
- Leaking from base — tank shell failure. Replace, don't repair. Leaking
- Tankless throwing error code — see brand-specific error code hubs: Rinnai, Navien, Rheem
Finding a qualified water heater technician
- Licensed plumber in your state (check the licensing board online)
- Manufacturer-trained for your brand if it's tankless or hybrid — Rinnai-trained, Navien Service Specialist, Rheem Pro Partner, AO Smith ProMax. Brand-trained technicians have direct phone access to engineering and faster parts
- Reviewed locally — Google, Yelp, and Nextdoor are reliable for water heater work. National "find a pro" sites often funnel to whichever contractor pays the most
- Itemized quote — diagnostic fee, parts, labor separately
- Warranty on the repair — at minimum 90 days on labor, 1 year on parts
Emergency repair situations
Stop the water and gas/electric BEFORE you call:
- Turn off the cold-inlet valve on top of the heater
- Turn off gas at the unit's shutoff (gas) or flip the breaker (electric)
- If it's actively flooding, drain the tank via the drain valve to a hose and floor drain
- Then call for service — same-day plumbers exist in most US metros
Repairs under warranty
If your unit is inside its warranty window, repair through the brand's authorized installer network — not through a random plumber. The brand pays parts (and labor in year 1 for most brands); a non-authorized repair voids the warranty for the affected system. Check warranty status via the brand-specific warranty pages:
Related guides
- Installation
- Replacement
- Maintenance — preventing the next repair
- Parts directory
- All problems
Bottom line
Most water heater repairs cost $80-400. Diagnose the symptom yourself before calling — it saves the service-call markup. If the unit is over 10 years old and the repair quote exceeds $400-500, replace instead. Stay inside the brand's authorized installer network for any work inside the warranty period.