Rheem Water Heater 12: Official Meaning and Checks
Direct answer
What 12 means
Official Rheem material describes 12 as LP gas is running low (LP models only). This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Before you begin
Safety first
LP models only; follow the manual's gas safety instructions.
- Record the complete displayed code and the full model number before clearing the display.
- Disconnect power before touching a user-accessible filter, hose, burner, or electrical connection.
- Stop using the equipment if it leaks, smells burned or of gas, smokes, sparks, or trips a breaker.
Does this guide apply?
- Region
- United States
- Product family
- Rheem RTGH condensing series (manual covers 120,000-199,900 Btu/hr condensing direct-vent models; product page RTGH-90DVLN-3)
- Exact models
- Not listed in the cited source. Confirm the full model in the official manual.
- Scope note
- The cited source scope is Rheem RTGH condensing series (manual covers 120,000-199,900 Btu/hr condensing direct-vent models; product page RTGH-90DVLN-3). Confirm the complete model number before applying the guidance; an empty model list does not imply all models.
Find the model label and official manual before ordering a part
Common paths to check
These are source-backed possibilities, not probability estimates for your specific unit.
- 01 Official source meaning: LP gas is running low (LP models only).
Decision path
Safe checks, in order
- 1
Confirm code and model scope
Compare the complete display and full model number with the cited manufacturer page or manual before applying any troubleshooting instruction.
Expected: The official source explicitly covers the displayed code and product family.
If not resolved: Contact manufacturer support with the full model and serial number.
- 2
Follow the official owner checks
Refill or replace your LP gas container.
Expected: Only the user-accessible condition identified by the official source is corrected.
If not resolved: Stop repeated resets and arrange qualified service if the code returns or the source directs service.
Reset and test
- Yes - official procedure: turn off the water heater, unplug for about 30 seconds, plug back in, restart, and recheck (manual page 74).
Important: A reset may clear the display but cannot repair the underlying condition; follow only the exact model-specific manufacturer procedure.
Escalation point
Stop and arrange service when
- LP models only; follow the manual's gas safety instructions.
- The equipment leaks, smells burned or of gas, smokes, sparks, overheats, or trips a breaker.
Model-first repair planning
Components that may be involved
The items below describe the documented diagnostic path. They are not a diagnosis and do not identify a compatible replacement part without the complete model and original part number.
- LP gas container
Official sources
We paraphrase manufacturer material and show the publication scope so you can verify it.
- Rheem RTGH series Use and Care Manual, Service Error Code Chart, PDF page 75 Rheem · 12 · accessed 2026-08-08
Reviewed by Device Fix Guide · Last source check:
Related guides for this equipment
These links share the same brand and equipment family. A related guide does not prove that the codes have the same cause on your model.
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