Why Is My Rheem Water Heater Not Heating?
On this page (7 sections)
The Short Answer: Start by identifying which Rheem you have. Electric tanks usually have a tripped breaker, a tripped high-limit, or a failed element or thermostat. Gas tanks usually have a pilot or ignition problem, a gas supply issue, or a lockout shown by the status light. Heat pump and tankless models show their own codes. Hot tank, lukewarm taps points to a mixing valve or dip tube.
Identify your Rheem
The rating plate on the side of the heater lists the model number and whether it is gas or electric. Rheem, Ruud and Richmond share many designs, so parts and procedures often overlap, but check your exact model in the Rheem owner support (opens in a new tab) or your manual.
| Type | How to recognize it | Most common no-heat causes |
|---|---|---|
| Electric tank | Two small access covers on the side, no vent | Breaker, high-limit (ECO), element, thermostat |
| Gas tank, atmospheric | Metal vent pipe and draft hood on top, gas control with a knob | Pilot out, gas supply, thermocouple or thermopile, control lockout |
| Gas tank, power vent | Blower on top, plastic vent, plugged into an outlet | Power, vent blockage, pressure switch, ignition |
| Heat pump (hybrid) | Fan and compressor on top, digital display | Operating mode, filter, error code, element backup |
| Tankless | Wall-mounted, numeric code display | Gas supply, flow, venting, codes |
Electric tank: cold or only lukewarm
No hot water at all: check the breaker first. If it is on, the high-limit switch on the upper thermostat may have tripped, or the upper element may have failed. These are behind covers with live 240-volt parts, so a technician should test them. If the breaker keeps tripping, see breaker tripped and won’t reset.
Some hot water but it runs out fast: the lower element or lower thermostat is the most common cause. See water heater element not working.
If the high-limit trips repeatedly, something is overheating, often a thermostat stuck on or a grounded element. See why you keep having to reset.
Gas tank: no burner
Look through the sight glass at the bottom of the heater:
- Pilot out: relight following the instructions on the heater’s label. If it won’t stay lit, see Rheem pilot light won’t stay lit.
- Status light flashing a count: Rheem gas controls report faults by flash count, and the chart is on the control’s label. Rheem-specific pages cover several of them, such as Rheem water heater won’t light and Rheem gas control or valve failure.
- Pilot lit but burner never comes on with the dial turned up: the gas control or thermopile may be weak; see Rheem thermopile voltage low.
Confirm the gas supply valve to the heater is open and that other gas appliances work. If you smell gas, leave and call the gas utility from outside.
Heat pump and tankless models
A Rheem heat pump water heater can be slow because of its operating mode, a dirty air filter, or a cold room, and it shows error codes on its display. See Rheem heat pump water heater problems. For Rheem tankless units, record the code on the display and see Rheem tankless troubleshooting.
When the heater is fine but the taps aren’t
If the pipe leaving the heater is hot but the taps are lukewarm, look downstream: a mixing valve at the heater, a shower cartridge, or a crossover where cold water is getting into the hot line. On a tank, a broken dip tube lets incoming cold water mix at the top, which gives a short burst of hot water followed by lukewarm water.
What the technician will check
Electric: element and thermostat tests, high-limit, wiring and breaker. Gas: gas pressure, pilot and burner, thermocouple or thermopile output, and the control’s fault history. In both cases they will look at the tank’s condition and age before recommending parts.
Frequently Asked Questions
Q: Where is the reset button on a Rheem water heater? A: On electric tanks, it is the red button on the upper thermostat, behind the upper access cover with live 240-volt parts. Have a technician reset it after finding out why it tripped. Most gas tanks do not have a similar button; they are relit following the label.
Q: My new Rheem only gets lukewarm. Is it defective? A: Check that the temperature setting was not left low and that the heater has had time to fully heat. On new installations, a mixing valve setting or reversed hot and cold connections are common causes.
Q: Should I turn my Rheem up higher to get more hot water? A: Only a little, if at all. Raising the setting increases scald risk and does not fix a failed element, pilot or thermostat.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- Rheem: owner help and support (opens in a new tab)Identify the applicable model instructions or contact Rheem support.
- A. O. Smith: standard electric no-hot-water diagnostic chart (opens in a new tab)Professional diagnostic context for standard electric storage heaters; not instructions to open or test your appliance.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
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