For a gas water heater, leave it on On for normal use and switch to Pilot only for short absences or troubleshooting; turn it fully off for long trips or service. Pilot mode is the setting that keeps the small pilot flame burning while the main burner stays off.
The most common mistake is flipping the knob to Pilot every night or every time you leave the house for a few hours. That saves very little gas, and it can leave you with lukewarm water and an unnecessary relight chore when you come back.
If your heater is electric, the answer is simpler: there is no pilot flame at all, so this question only applies to gas models. Modern gas units may also use electronic ignition, which changes the maintenance question a bit.
Water Heater Pilot Mode Versus On Mode Explained
Keep a gas water heater on On for normal daily use; use Pilot for a short absence when you want to save gas without making relighting difficult. The pilot light should stay lit on a standing-pilot heater, while the main burner fires only when the tank needs heat, so the pilot and burner don’t stay on continuously.
Understanding the settings helps optimize your water heater's efficiency.
In short
Leave the water heater on On while you’re using hot water regularly. Turn the control to Pilot for a short trip, and to Off for a long absence, service, or draining the tank.
Setting
Best use
Gas use
Convenience
Pilot
Short absence or brief troubleshooting
Pilot flame only; lower than On
Easy restart because the pilot stays lit
On
Normal daily living
Pilot plus main burner as the tank calls for heat
Hot water is maintained and available
Off
Long trip, service, or draining the tank
No burner or pilot gas use
You’ll need to relight and restart it
These settings apply to a gas heater with a standing pilot. Follow the label on your specific control valve.
For a weekend away, Pilot is usually the sensible middle setting: the small flame remains available, but the main burner won’t heat the tank. For a long trip, turning the heater Off saves more gas, though relighting may be inconvenient and service work should follow the manufacturer’s instructions. A licensed professional should handle gas connections or repairs.
Don’t cycle it every night
Leave the heater on On if you use hot water each day. Switching between Pilot and On every evening saves little, adds chances to misread the knob, and can leave you without hot water when you need it.
If your heater has a standing pilot, the small pilot flame is expected to stay on. The larger burner flame should come and go; a burner that runs constantly, won’t light, or makes unusual noise needs attention rather than a different knob setting.
What The Pilot Setting Actually Does
Pilot mode keeps only the small pilot flame alive; On lets the gas control valve use that flame to ignite the main burner when the tank needs heat. Set a tank or tankless heater to about 120°F as a common starting point, then follow the appliance manual and adjust for your household’s needs because hotter water raises scald risk.
Inside a standing-pilot tank heater, the control valve monitors water temperature through its thermostat. In Pilot, the valve blocks the main burner; in On, it opens the main gas path during a heating cycle, then closes it when the set temperature is reached. The pilot itself adds very little heat to the tank.
3.6 therms
Example monthly pilot gas use
A hypothetical pilot rated at 500 Btu per hour uses 500 × 24 × 30 = 360,000 Btu in 30 days, or 3.6 therms. At an assumed $1.50 per therm, that would be about $5.40 for the month.
Worked example
Say the label on a standing pilot lists 500 Btu/h. The pilot runs whether the knob is on Pilot or On, so its baseline is 500 × 24 × 30 = 360,000 Btu, or 3.6 therms, over a 30-day month. On adds the gas used by the main burner whenever the tank reheats; the actual amount depends on hot-water use, insulation, incoming water temperature, and the heater’s efficiency.
Pilot rating500 Btu/h
Monthly time720 hours
Monthly pilot gas3.6 therms
Assumed gas rateabout 1.5 therms
Setting
What burns
Hot-water comfort
Pilot
Standing pilot only
The tank gradually cools; the main burner won’t reheat it
On
Pilot plus main burner as needed
The tank reheats automatically and is ready for normal use
On doesn’t mean the large burner runs nonstop.
Many newer gas water heaters use electronic ignition, so they light the burner only when a heating cycle begins and don’t need a standing pilot. Tankless heaters also commonly use electronic ignition because they heat water as it flows, while heat pump water heaters use electricity and a compressor rather than a gas pilot. For a closer look at the control sequence, see what the Pilot setting does on a water heater; for temperature guidance, see the best water heater temperature.
What You May Need
Only if the pilot keeps going out or the assembly is worn.
Pilot keeps going out
A. O. Smith Natural Gas Pilot Assembly
If the pilot won’t stay lit and the assembly is visibly worn, this natural-gas pilot assembly may fit the repair. Confirm your water heater’s compatibility before ordering; a replacement part won’t fix a bad thermocouple, gas control, or ventilation problem.
Use Pilot for a short absence, On for normal use, and Off for long shutdowns or service. A weekend away rarely saves enough gas to justify the relighting hassle, while a month away usually makes Off the better choice.
Situation
Best setting
Reason
Weekend away
On or Pilot
Pilot saves a little gas, but the saving over two or three days is small.
About one week away
Pilot
The tank won’t call for the main burner, while the pilot keeps relighting simple.
About one month away
Off
Avoid the standing pilot cost and shut the appliance down before extended service or draining.
Caravan or RV
Follow the appliance manual
The pilot shouldn’t stay lit unless that water heater is approved for the vehicle and the gas system’s instructions allow it. Turn it off before travel.
The manual and local rules take priority over a general setting rule.
Turning the pilot off completely stops the flame and prevents the burner from heating the tank; you’ll need to relight it before making hot water. During summer, keep the manufacturer’s setting unless you’re changing the temperature for a specific reason; around 120°F at the tap is a common target, and scald risk rises above that.
Before You Leave
Set the control to Pilot for a short trip or Off for a long absence.
Close the manual gas shutoff valve if the manual calls for it, and always close it before service or draining.
Reduce house risks, including leaks, open flames and unattended fuel-burning appliances.
Keep freeze protection in mind: shutting the heater off won’t protect exposed plumbing in a cold garage or vacant house.
Leave ventilation and the working CO alarm in place; never leave an indoor gas heater unvented or unattended when its manual says otherwise.
Draining The Tank
Pilot mode alone isn’t enough for draining. Turn the gas control off, close the manual gas valve, let the water cool, and follow the heater’s draining instructions; a hot tank can scald you and an open gas valve can leave the appliance ready to fire.
In short
Pilot suits a short absence when you want easy restart. Off suits extended shutdowns, service and draining, but winter plumbing still needs separate freeze protection.
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How Cost, Emissions, And Comfort Compare
Pilot costs less than On because only the small flame burns, but On is the better setting for hot-water availability; the best balance is On during normal use and Pilot only when the tank will sit idle for several days.
Setting
What burns
What you get
Pilot
The standing pilot only
Lower gas use, no normal recovery, and slower return to usable hot water.
On
Pilot plus burner cycles as the tank cools
Fast recovery and hot water ready when the tank reaches its set temperature.
Off
Nothing
No gas use from the heater, but no heat and a relighting step later.
The actual On-mode cost depends on hot-water use, tank losses and the heater’s input rating.
A simple illustration shows the scale: a pilot rated at 1,000 Btu per hour uses 0.01 therm per hour, or 7.2 therms in 30 days; at an assumed $1.50 per therm, that is 7.2 × $1.50 = $10.80. Your rating plate and gas bill control the real number, while normal burner cost varies with showers, laundry, incoming water temperature and insulation.
Where The Bigger Saving Lives
Pilot cuts burner cycling only while the tank would otherwise sit idle; it doesn’t make water heat faster. Less gas burned means less carbon dioxide, but reducing tank heat loss usually matters more than changing Pilot and On for a short trip. A jacket may help an older tank if the manufacturer allows it; don’t cover a newer foam-insulated tank when its label says no.
Domestic water is commonly maintained around 120°F at the tap for a practical safety and comfort balance. On gives the burner permission to recover the tank promptly; Pilot leaves only the small flame working, so the first shower after an empty tank can wait.
Safety, Lifespan, And Pilot Troubleshooting
A missing red light doesn’t automatically mean your water heater has failed: indicator behavior varies by model, and a blinking red light may be a diagnostic code listed on the label. Some clicking, ignition whooshing, or mild expansion sounds can be normal, but a persistent buzz, loud popping, rumbling, or gas smell needs attention. Standard gas tank heaters usually have metal venting; PVC vent pipe belongs only on a model whose manufacturer lists it.
Check the indicator light for potential issues before troubleshooting.
1
Watch the pilot flame
A healthy pilot is steady and strong enough to contact the flame sensor. A tiny yellow, wavering, or repeatedly disappearing flame points to a dirty pilot tube, a worn pilot assembly, poor gas supply, or a thermocouple that isn’t sensing heat.
2
Understand the safety shutdown
The thermocouple sits in the pilot flame and produces a small electrical signal while it is hot. If the pilot goes out, that signal stops and the gas control shuts the valve, preventing unburned gas from continuing into the burner.
3
Check the pattern
A pilot that lights but won’t stay lit often indicates the thermocouple, pilot assembly, or gas control. A burner that never starts after a steady pilot may point to the thermostat or valve. Don’t keep holding the knob down or repeatedly resetting a heater that fails.
For a worn natural-gas pilot assembly
A.O. SMITH 9003542005 Water Heater FV Pilot
Product 1 is a replacement 9003542 natural-gas pilot assembly for a compatible A. O. Smith water heater; match the heater’s exact model and existing part number before ordering.
Smell gas, see soot around the burner or flue, hear a persistent buzz from the gas control, or lose the pilot repeatedly? Turn the control to Off if you can do so without operating near a gas cloud, leave the area, avoid switches and flames, and call a licensed professional or your gas utility. Never clean a gas orifice with a wire or alter the venting.
PVC needs a listing
PVC may be used for water connections on some installations if the material and local code allow it. PVC flue pipe is different: use it only when the water-heater manual and listing specifically approve it, which is usually not the case for a standard atmospheric gas tank.
What To Do Next
Set a new or existing water heater to about 120°F at the tap unless the manufacturer or a qualified professional gives you a different instruction; hotter water increases scald risk, and there isn’t one universal highest setting that’s safe for every home.
Before touching the control
Stop if you smell gas, see soot, or hear an unexplained loud buzz.
Check that the manual gas shutoff valve is open and read the lighting instructions on the heater.
Check for freeze risk if the heater is in a garage, crawlspace, or vacant home.
Confirm that it is a gas tank heater; electric and tankless units use different controls and must follow their appliance labels.
1
Normal daily use
Leave the gas control on On so the burner can heat the tank whenever the thermostat calls for heat.
2
Short vacation
Use Pilot only for a brief absence when the manual permits it and you want to keep the pilot lit with less gas use.
3
Long absence or service
Use Off for a long shutdown or before service, but protect nearby plumbing from freezing and don’t disconnect gas fittings yourself.
4
Pilot won’t stay lit
Stop repeated attempts, follow the lighting procedure exactly once the area is safe, and arrange service if the flame goes out again. Relight or restart only as the manual directs.
A conventional gas water heater needs its pilot light on whenever you want the burner ready to heat water. If the pilot keeps going out, stop repeated relighting and follow the model’s troubleshooting instructions; a blocked vent, faulty thermocouple, or gas-control problem needs attention. Electronic-ignition and electric models may have no pilot light at all.
Should the water heater be left on pilot or on during vacations?
For a short absence, Pilot can reduce gas use while keeping relighting simple. For a longer trip, Off saves more gas, but check the manual and protect the plumbing from freezing before shutting the heater down. Leave the setting on On if people will need hot water while you’re away.
What happens if the pilot light is turned off completely?
The main burner won’t operate, so the tank will stop reheating water after its stored heat runs out. You’ll also need to relight the pilot using the manufacturer’s procedure before normal operation returns. If the water heater is being serviced, a qualified professional should handle the gas shutoff and restart steps.
How do energy costs compare between leaving the heater on pilot vs. on?
Pilot uses only the small flame, while On allows the burner to run whenever the tank loses heat or someone uses hot water. The dollar difference depends on the pilot’s gas rate, tank insulation, water use, incoming water temperature, and your gas price, so one universal savings figure would be misleading. Compare gas-meter readings over equal periods, or use the manufacturer’s annual gas-use figure for a closer estimate.
Do modern water heaters require pilot lights or use electronic ignition?
Many newer gas water heaters use electronic ignition, which lights the burner only when heat is needed and doesn’t maintain a standing pilot. Electric water heaters use heating elements, and heat pump water heaters move heat with a compressor, so neither uses a gas pilot light. Check the data plate and owner’s manual before looking for a pilot control that may not exist.
Should you put a jacket on a hot water heater if it is in a garage?
Only add an insulation jacket if the manufacturer permits it and the jacket is sized for that model. Keep the gas control, burner access, vent, air openings, drain, and T&P valve discharge line uncovered; blocking any of them can create a safety problem. A jacket won’t solve freezing pipes or a poorly vented garage, and it isn’t appropriate for every newer tank.
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