No hot water at any tap usually means a single-cause failure at the water heater. The diagnostic depends on what type of water heater you have, because gas tank, electric tank, and tankless systems all fail differently. First step is identifying your unit type, then walking through the type-specific checks. About a third of "no hot water" calls turn out to be issues homeowners can fix themselves (relighting pilot, resetting breaker, etc.) — the rest need professional service.
Most common causes
The likely culprits, roughly in order of how often we see each one:
- Gas tank: pilot light out
Older gas tank water heaters with standing pilots can blow out from drafts, condensation, or thermocouple failure. Newer units with electronic ignition fail differently — ignition module, gas valve, or sensors.
- Gas tank: thermocouple failure
The thermocouple is a safety device that detects whether the pilot is lit. If it fails, it shuts off the gas valve even when pilot is healthy. Pilot won't stay lit. Replacement: $200-$350 service call.
- Electric tank: tripped breaker or failed heating element
Electric water heaters have two heating elements (upper and lower) and corresponding thermostats. Failed element is the most common issue; tripped breaker happens when something stresses the system. Element replacement: $300-$550.
- Tankless: ignition failure or error code
Tankless units self-diagnose and display error codes on the front panel or remote. Common codes: 11 (ignition failure), 12 (flame failure), 14 (overheating), 99 (vent issues). Code points directly to fix needed.
- Tank water heater: tank is leaking
A leaking tank can't maintain water level, so heating elements or burners can't do their job. Also a same-day-replacement situation regardless — leaking tanks tend to leak faster as time goes on.
- No fuel/power supply
Gas turned off (utility issue, valve closed), breaker tripped, or for tankless: the dedicated electrical circuit failed.
- Sediment buildup at bottom of tank
Sediment insulates the burner from the water it's supposed to heat. Result: water heater runs but produces less hot water and what comes out is lukewarm. Tank flush sometimes resolves; old tanks usually past the point of recovery.
What to check yourself first
Before calling, walk through these — sometimes the fix is something simple:
- Identify your water heater type
Tank water heater (4-6 ft tall cylinder) vs tankless (wall-mounted box, 16-20 inches square). For tank: gas (has a vent pipe and gas line) vs electric (has a heavy power cable but no vent). For tankless: gas-fired or electric.
- Gas tank: check the pilot light
Most have a viewing window near the bottom. Pilot lit (blue flame) = pilot OK; out = relight per the instructions on the side of the tank. Won't stay lit after relighting = thermocouple issue, call for service.
- Electric tank: check breakers
Electric water heaters use a 30-amp double-pole breaker. If tripped, reset once. If it trips again immediately, stop — call for service (likely a heating element shorted).
- Tankless: check error code
LED display on front of unit shows error code. Match to the manual or note the code for your service call. Many error codes have homeowner-fixable causes (clear vent obstruction, replace inline filter).
- Check for visible leaks
Walk around the water heater. Any water on the floor, dampness on the tank, or rust streaks? Tank leak = same-day replacement situation.
- Check the temperature setting
Thermostat dial on tank units, control panel on tankless. Set to 120°F (49°C) typically. If accidentally turned to "vacation" or low, that's the issue.
What NOT to do
- Don't keep relighting a pilot that won't stay on — the thermocouple is failed and the gas valve is closing for safety
- Don't reset the breaker repeatedly if it trips immediately each time — there's a real electrical issue
- Don't try to replace heating elements on an electric water heater unless you know how to drain the tank and verify power is off
- Don't ignore a leaking tank for "a few more days" — leaks accelerate fast
When to call us
Stop troubleshooting and pick up the phone if:
- Pilot won't stay lit after multiple relighting attempts
- Tank is visibly leaking
- Breaker keeps tripping after you reset it once
- Tankless showing error code that doesn't clear
- Water heater is over 10 years old and failing for the first time
- Hot water comes out brown, smelly, or with sediment
- You smell gas anywhere near the water heater (call us AND turn off the gas)
Frequently asked questions
Why is my hot water lukewarm but not cold?
Usually one of three things: thermostat set too low (easy fix), heating element partially failed on electric tanks (one of two elements out — replace the failed one), or sediment buildup insulating the burner from water on gas tanks. Sediment-related issues sometimes respond to a tank flush; long-standing sediment usually means the tank is near end of life.
How fast can you replace a water heater?
Same-day for most tank water heater replacements if we have the right unit in stock. Standard 40 or 50-gallon tank: 3-4 hours. Heat pump water heater: 4-6 hours. Tankless: 6-10 hours (more complex install). For emergency leak situations, we prioritize same-day replacement.
Should I just replace my old water heater rather than repair?
Generally yes if the unit is over 10 years old. Tank water heaters typically last 10-14 years; major repairs (heating element, gas valve, thermocouple) on a 12-year-old tank often don't pay back since the tank itself is near end of life. Newer units (under 8 years), repair is usually the right call.
My water heater is rented — what do I do?
Rented water heaters from Reliance, Enercare, etc. include service in the rental. Call your rental company first — they'll dispatch their own technician. Worth noting: at the end of your rental contract, buying a new water heater and owning it usually costs less over a 5+ year horizon than continuing to rent.
Related services
If you need professional repair, the relevant services for this issue: