Hot water not working but cold water is: causes
Short answer
If cold water works but hot does not, first check whether it is every fixture or just one. Every fixture points to the water heater: a pilot out, a tripped breaker or reset, a failed element or thermostat, or an error code on a tankless unit. One fixture only points to that faucet or shower valve, often a stuck cartridge or anti-scald limit.
In this guide
Cold water flowing normally tells you the water supply is fine. The problem is on the hot side, and the first clue is how widespread it is.
Every hot tap: check the water heater
| Heater type | Check first |
|---|---|
| Gas tank | Is the pilot lit? Is the gas valve on? Any status light code? |
| Electric tank | Breaker on? High-limit reset button tripped? |
| Gas tankless | Error code on the display? Gas and power on? |
| Electric tankless | Breakers on? Enough flow to activate? |
Common causes
- Gas tank: pilot out from a bad thermocouple or thermopile, gas valve problems, a flammable vapor sensor lockout.
- Electric tank: a failed upper element or thermostat, or a tripped high limit.
- Tankless: ignition failure codes, a clogged inlet filter, low gas supply, a failed flow sensor.
- Any heater: a closed hot water outlet valve after recent work.
If you smell gas, do not touch switches or light anything. Leave the house and call your gas utility from outside.
Electric water heaters run on 240 volts. Turn off the breaker and confirm the power is off before opening any access panel.
One faucet or shower only
- A clogged or stuck cartridge in that faucet or shower valve
- An anti-scald limit stop set too low on a shower valve
- A clogged aerator on the hot side
Look up any error code first. Our brand error code pages list what each one means, and the water heater repair cost guide covers prices.
What to tell the plumber
- Your heater type, brand and approximate age
- Whether the problem affects every fixture or just one
- Any error code, status light pattern or tripped breaker
- Whether it started after a power outage, storm or plumbing work
With that information, the technician often knows which parts to bring, saving a second visit. For brand-specific codes, see our Rinnai, Navien, Rheem, Noritz, A. O. Smith and Bradford White pages.
Common questions
Why do I have hot water in one bathroom but not another?
The problem is probably that fixture's valve or cartridge, not the water heater.
Can a tripped breaker cause no hot water?
Yes, on electric water heaters. Reset it once; if it trips again, see our guide to a water heater tripping the circuit breaker.
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