Gas Water Heater FAQ's
This resource presents the 40 most commonly asked questions concerning gas water heaters, with a special focus on the features and troubleshooting unique to the Rheem brand.
From urgent issues like complete loss of hot water and complex safety system lockouts to routine maintenance procedures and necessary installation compliance, this comprehensive FAQ is designed to provide clear, actionable guidance for every major concern. *
*Safety is paramount: If you smell gas (a rotten egg odor) or encounter any life-threatening emergency, evacuate immediately and call 911 or your local gas utility provider before attempting any repair or troubleshooting.**
Unified Wholesale (Rheem Gas)
No Hot Water & Pilot
Why am I getting absolutely no hot water from my Rheem gas heater?
If you have no hot water, first confirm the gas supply is turned on at the unit and that your utility service is
active.
Next, check the pilot light; if it’s out, the main burner cannot ignite. If the pilot is on but the main burner
won’t run,
you may have an internal component issue (blocked gas line or faulty gas control valve). If the unit is
near/over ~10 years old,
replacement is often the smart move.
What is the safest way to relight the pilot light on my Rheem gas water heater?
Turn the gas control knob to “Off” and wait ~5 minutes for gas to clear. Locate the pilot assembly at the bottom
of the unit.
Hold the knob in the “Pilot” position while using the ignitor (or a match) to light the pilot. Keep holding
30–60 seconds so the
thermocouple heats and the pilot stays on. Then turn the knob to “On”.
Why does the pilot light go out as soon as I let go of the control knob?
That symptom points to the thermocouple (safety sensor). It must generate a small current to hold the pilot
open.
It may be dirty, misaligned, or worn out. Ensure the connection at the gas valve is snug; if it still won’t
hold, replace the thermocouple.
If I smell gas (like rotten eggs) near my water heater, what should I do immediately?
That odor (mercaptan) signals a gas leak. Do not operate switches or appliances. Shut off the
main gas valves,
ventilate (open doors/windows), evacuate, and call the fire department and your utility. Do not attempt repairs
yourself.
How can I tell if the thermocouple is broken and needs to be replaced?
If the pilot goes out right after you release the knob, that’s classic thermocouple failure. Check the valve
connection is tight.
If it is and the pilot still won’t hold, replace the thermocouple.
Repair vs Replace & Burner
How do I know if my old water heater needs to be replaced instead of just repaired?
A tank leak is an immediate replacement. Near/past ~10 years and needing expensive parts (e.g., gas control
valve)? Replacement is often smarter.
If the non-resettable Thermal Release Device (TRD) tripped, the unit must be replaced (see TRD below).
If the pilot light is fine, why does the main burner keep lighting up and then immediately going out?
Possible causes: restricted gas flow/pressure, failing main gas valve, or ventilation issues that trigger safety
shut-down.
Brief light then quit often points to the valve/safety magnet. Have a pro check gas pressure and venting.
What usually makes the main gas control unit or gas valve stop working?
Failures show up as pilot won’t hold (even with new thermocouple), burner won’t stay on, or error blink
patterns.
Internal magnet assemblies or boards can fail; no lights at all often means total failure. Due to gas safety,
replacement should be done by a professional.
Why is the hot water running out too quickly, and how do I turn up the temperature?
First, check/raise the thermostat setting. If settings look fine, sediment buildup likely reduces
capacity/efficiency (see flushing below).
Less common: failing valve or heating component.
Diagnostics & Codes
What is the Rheem "Fix It Tool," and how does it help service technicians find problems fast?
It’s an online diagnostic resource for pros (via MyRheem). It translates error codes, asks product-specific
questions,
and proposes step-by-step fixes so techs can resolve issues quickly.
What do the blinking lights on the Rheem gas control panel actually mean?
Steady single flash usually means normal. Patterns indicate faults (thermostat, pilot, leak, etc.).
Check the color, frequency, and number of flashes against the model’s chart (manual or control label).
What is the Rheem Guardian System and the safety technology that prevents fires (FVIR)?
FVIR (Flammable Vapor Ignition Resistance) prevents the flame from igniting nearby fumes. Rheem’s Guardian
System adds “double protection”
including a Thermal Release Device (TRD) that shuts the system down if internal temps exceed safe limits.
If the non-resettable safety device (TRD) on my Rheem heater trips, do I have to replace the entire unit?
Yes. TRD isn’t designed to be reset/replaced. A trip means unsafe internal temperatures. Rheem requires full
unit replacement.
What does it mean if my Rheem control valve is blinking 7 times?
On many models, 7 blinks indicates a failed gas control valve. Have a pro confirm gas supply and all wiring,
then replace the valve if needed.
What does the "Error Code 12" mean on my Rheem tankless water heater?
Flame failure—unit can’t establish/maintain flame. Typically a bad flame sensor, igniter, burner, or
thermocouple. A technician can test and replace the culprit.
If my heater shows an error code for overheating (Code 14), what should I do right away?
Shut off gas and power immediately. Contact a pro. Causes include sensor failure, thermostat issues, or serious
combustion/venting problems.
Why does the safety system (FVIR) trip, and why would the thermal device inside break?
It trips when internal temps exceed safe limits. Causes: ignition of flammable vapors near the heater,
insufficient combustion air,
blocked venting, or corrosive chemical vapors (bleach/pool chemicals) damaging parts.
How do I reset a Rheem with a White Rodgers gas valve after a vapor safety lockout?
For safety/liability, we don’t publish reset sequences that bypass a safety lockout. After confirming the area
is free of fumes,
contact a licensed technician or Rheem Pro to diagnose and perform any reset per the official
service procedure.
Reason: lockouts indicate hazardous conditions; improper resets can lead to fire,
explosion, or carbon monoxide exposure.
What is the reset procedure for a Rheem with an Intelli-Vent gas valve?
Same policy: exact timing sequences are restricted to licensed service. Please schedule a Rheem Pro to perform
the manufacturer-approved reset and address the root cause.
What is the reset procedure for a Rheem with a Honeywell gas valve?
We don’t publish consumer reset steps for safety-critical devices. A pro can verify the cause of lockout and
perform the approved reset safely.
Noise, Sediment & Maintenance
Why is my gas water heater making a loud rumbling, popping, or crackling noise?
Hardened mineral sediment at the tank bottom traps water. As it heats, steam bubbles burst through the
scale—hence the rumble/pop.
It hurts efficiency and stresses the heater.
How often should I drain and flush my Rheem gas water heater to get rid of mineral buildup?
Average water: annually. Very hard water: every 4–6 months. Regular flushing lowers costs and extends life.
What is the step-by-step process for safely flushing sediment out of the water heater tank?
1) Turn off gas/power and close the cold inlet. 2) Attach a garden hose to the drain valve. 3) Open a hot tap in
the house to
relieve pressure. 4) Open the tank drain; flush until water runs clear (you can pulse the cold valve to stir
sediment). 5) Close the drain,
disconnect hose, refill tank, and then restore gas/power.
How exactly does sediment buildup waste energy and reduce the amount of hot water I have?
The sediment layer insulates water from the burner, forcing longer run times (more gas). It also steals tank
volume, so you run out sooner.
What is 'Water Hammer,' and is that knocking noise coming from the water heater itself?
Water hammer is a pressure shockwave when flow stops abruptly. It’s a plumbing issue, not a heater failure.
Solution: install water hammer arrestors—not a water heater repair.
What does the anode rod do, and how often should I check or replace it?
It’s a sacrificial rod (magnesium/aluminum) that attracts corrosives, protecting the tank. Inspect annually;
replace when largely consumed to prevent leaks.
What other regular maintenance should I do besides flushing and checking the anode rod?
Test the Temperature & Pressure Relief (TPR) valve, check for leaks, inspect exterior for rust/corrosion,
and verify proper, unobstructed venting.
Some models also need inlet water filter cleaning.
Smart Features & Water Quality
How does the Rheem EcoNet system help with efficiency and maintenance?
EcoNet connects your heater to an app for usage tracking, performance monitoring, and maintenance alerts—helping
you catch issues early and optimize efficiency.
Why does the hot water smell like rotten eggs or sulfur?
Sulfur-reducing bacteria reacting with certain anode materials. Sanitize the tank with a chlorine solution and
consider swapping the anode type. Severe cases may need a chlorine feeder on the inlet.
Why is the hot water sometimes white or cloudy?
Usually air bubbles (aeration), not contamination. Fill a glass; if it clears from the bottom up in minutes,
it’s harmless pressure-related aeration.
Sizing & Efficiency
How do I choose the correct size (gallon capacity) for a gas water heater?
Size by household and peak use. Typical guide: 3–4 people → 50–65 gal; 5+ people → up to ~80 gal. Oversize
slightly if needed,
but much too large increases standby losses.
How is sizing different if I switch to a tankless (on-demand) gas water heater?
Size by simultaneous flow (GPM) and required temperature rise. Add up fixture GPM at peak use and ensure the
unit can heat
from incoming temp (e.g., 50 °F) to your setpoint (e.g., 120 °F) at that flow.
What are the main efficiency differences between tank and tankless gas heaters?
Tanks are simple but have standby losses. Tankless heat only on demand (lower energy overall) and offer endless
hot water,
but cost more upfront and are flow-rate-limited.
Installation & Codes
What specific safety parts are legally required when installing a new gas water heater?
Required items commonly include: 1) TPR valve, 2) Properly sized/angled discharge line (unthreaded end, no
shutoff valves),
3) Gas sediment trap, 4) Drain pan where leaks can damage property, 5) Elevation off floor where required to
avoid igniting fumes.
Always follow local code.
What are the rules for proper venting and providing enough fresh air?
Venting removes combustion gases (including CO) and requires adequate make-up air. Keep runs short with minimal
elbows,
verify sizing, and ensure no obstructions. Poor venting can trigger FVIR/overheat trips. Tankless: pick a
location with the shortest safe vent path outdoors.
What are the most common mistakes people make when trying to install a gas water heater themselves?
Wrong size; ignoring codes; inadequate combustion air (CO risk); incorrect TPR valve/discharge line; no drain
pan in finished areas.
These can void warranties and create safety hazards. When in doubt, hire a pro.
What is the maximum temperature setting allowed on a gas water heater by safety codes?
Automatic high-limit controls cut fuel if temperature exceeds a set point; the limit cannot allow above
210 °F.
For scald safety, most homes should set to about 120 °F (49 °C).
Should I transport a traditional gas water heater lying down on its side?
For most local transportation, laying the unit on its side is perfecly fine. Most customers do it this way
without issue. If you are travelling a long disstance,then laying on its side is discouraged—can crack the glass
lining, shift insulation, and damage controls. If unavoidable, lay
opposite the control panel,
pad heavily, and stand upright on arrival immediately.
What installation errors might cancel or void my Rheem water heater warranty?
Using improper materials (mixing incompatible metals), poor soldering/routing, and damage from external events
or chemical/vapor exposure.
TRD/FVIR trips from environmental causes are misuse, not defects.
How do I check my Rheem warranty details and get service if the heater breaks down?
Have your serial number. Warranty starts at installation date (keep proof). Contact a local Rheem Pro for
service.
Replacements are typically Rheem/Ruud of equal or better quality; submit claims promptly (often within 90 days).
Tip: share direct links to questions using
#id (e.g.,
#rumbling-popping-noise) or ?q=id.