How to Convert a Water Heater from Propane to Natural Gas
Updated February 25, 2026
What is involved in converting a propane water heater to natural gas -- orifice changes, gas line sizing, venting, and when a new unit makes more sense.
Overview
Switching from propane to natural gas is common when natural gas service becomes available in your area. The water heater needs different orifices because propane and natural gas burn at different pressures and BTU ratings. Propane operates at higher pressure (11 inches water column) than natural gas (7 inches WC) and has more BTUs per cubic foot. Swapping orifices without the correct conversion kit causes incomplete combustion, carbon monoxide production, and potential gas leaks. This is not a casual DIY job -- it involves gas work that must be done correctly.
What You'll Need
Safety First
- Gas orifice conversion is not a beginner DIY project. Incorrect orifice sizing causes incomplete combustion and carbon monoxide -- an odorless, deadly gas. If you are not experienced with gas appliance work, hire a licensed plumber or HVAC technician.
- Never run a propane water heater on natural gas (or vice versa) without converting the orifices. The flame characteristics are wrong and the unit produces dangerous levels of carbon monoxide.
- After any gas conversion, test all connections with soapy water for leaks and verify proper combustion (blue flame, no soot, proper draft).
Step-by-Step Instructions
- Determine If Your Unit Is Convertible
Not all water heaters can be converted. Check the data plate for the model number and look for a conversion kit from the manufacturer. Rheem, A.O. Smith, and Bradford White offer conversion kits for most of their tank models ($50-$100). Some units are certified for one fuel only and cannot be converted. The conversion kit includes new burner orifices, a new gas valve spring or regulator setting, and updated instructions.
Tip: If the water heater is more than 8 years old, buying a new unit rated for natural gas ($400-$800) is often more practical than converting an aging unit. The conversion cost plus the remaining lifespan may not justify the investment. - Get the Conversion Kit
Order the manufacturer's conversion kit specific to your model. It includes the correct orifice(s) for the main burner and pilot. Do not use generic orifices -- the BTU rating and hole diameter must match your specific burner. The kit also includes instructions for adjusting the gas valve regulator from propane pressure (11 inches WC) to natural gas pressure (7 inches WC). Some kits include a new gas valve label to indicate the converted fuel type.
Tip: The conversion kit part number is often in your owner's manual. If not, call the manufacturer with your model and serial number. They will tell you the exact kit needed or whether conversion is possible. - Swap the Orifices and Adjust the Regulator
Turn off the gas supply. Remove the burner assembly. Replace the main burner orifice with the natural gas orifice from the kit -- it has a larger hole diameter because natural gas flows at lower pressure. Replace the pilot orifice. Reinstall the burner assembly. Adjust the gas valve regulator to the natural gas setting per the kit instructions. Some gas valves have an internal adjustment; others require swapping a spring. Update the data plate label to indicate the new fuel type.
Tip: Natural gas orifices have LARGER holes than propane orifices. This seems counterintuitive, but natural gas is delivered at lower pressure and has fewer BTUs per cubic foot, so a larger opening is needed to deliver the correct heat output. Getting this backwards (propane orifice on natural gas) produces a dangerously weak flame. - Verify Gas Line Sizing and Connections
Natural gas and propane may require different gas line sizes. Natural gas typically needs a larger line because it flows at lower pressure. Verify the gas line from the meter to the water heater is sized correctly for the BTU demand. A plumber or gas technician can check this with a gas line sizing chart. If the existing propane line is too small for natural gas delivery, it needs upsizing -- $200-$600 depending on the run length.
Tip: The gas meter itself must also support natural gas. Your utility company installs the meter and regulator when you switch to natural gas service. Make sure this is done before converting appliances. - Test and Verify Safe Operation
Turn on the gas supply. Check every connection from the meter to the water heater with soapy water -- spray each fitting and watch for bubbles. Bubbles = leak. Tighten and retest. Light the pilot per the instructions. Verify: pilot flame is blue with a small yellow tip, main burner lights when the thermostat calls for heat, flame is blue (not yellow or orange), no soot on the burner or vent, and the draft hood pulls air upward (hold a match near it). Install a carbon monoxide detector within 15 feet of the water heater.
Tip: After conversion, monitor the unit for the first week. Check for gas odor, verify the flame color is still correct, and make sure the CO detector has not triggered. A properly converted unit operates identically to a factory natural gas unit.
Pro Tips
- Natural gas costs less per BTU than propane in most areas. A family spending $100/month on propane water heating typically spends $40-$60/month on natural gas for the same usage. The conversion pays for itself in months.
- When natural gas becomes available, most homeowners convert all gas appliances at once -- water heater, furnace, stove, dryer. Hiring a plumber to convert everything in one visit is cheaper per appliance than doing them separately.
- Some manufacturers void the warranty if a non-factory conversion kit is used or if the conversion is not performed by a licensed technician. Check the warranty terms before converting.
- Propane water heaters that are converted to natural gas should have the old data plate label covered with the new fuel label from the kit. This prevents future confusion about which fuel the unit uses.
- If you are building new or doing a major renovation, buy a dual-fuel rated water heater. Some models come with both orifice sets and can be configured for either fuel during installation.
When to Call a Pro
This is a job for a licensed plumber or HVAC technician in most cases. The gas work, orifice sizing, regulator adjustment, and combustion verification require expertise. A mistake produces carbon monoxide. Call a pro if you are not experienced with gas appliance work, if the gas line needs upsizing, or if you are unsure whether your specific model is convertible.
Frequently Asked Questions
When should I call a plumber to convert a water heater from propane to natural gas?
This is a job for a licensed plumber or HVAC technician in most cases. The gas work, orifice sizing, regulator adjustment, and combustion verification require expertise. A mistake produces carbon monoxide. Call a pro if you are not experienced with gas appliance work, if the gas line needs upsizing, or if you are unsure whether your specific model is convertible.
What are some expert tips to convert a water heater from propane to natural gas?
Natural gas costs less per BTU than propane in most areas. A family spending $100/month on propane water heating typically spends $40-$60/month on natural gas for the same usage. The conversion pays for itself in months. When natural gas becomes available, most homeowners convert all gas appliances at once -- water heater, furnace, stove, dryer. Hiring a plumber to convert everything in one visit is cheaper per appliance than doing them separately. Some manufacturers void the warranty if a non-factory conversion kit is used or if the conversion is not performed by a licensed technician. Check the warranty terms before converting. Propane water heaters that are converted to natural gas should have the old data plate label covered with the new fuel label from the kit. This prevents future confusion about which fuel the unit uses. If you are building new or doing a major renovation, buy a dual-fuel rated water heater. Some models come with both orifice sets and can be configured for either fuel during installation.
What tools do I need to convert a water heater from propane to natural gas?
You will need: Manufacturer's conversion kit (model-specific, $50-$100), Adjustable wrench and socket set (for burner assembly and gas connections), Soapy water in spray bottle (for leak testing), Manometer (for verifying gas pressure -- professional tool), Carbon monoxide detector (install after conversion).
When should I call a professional instead of doing this myself?
This is a job for a licensed plumber or HVAC technician in most cases. The gas work, orifice sizing, regulator adjustment, and combustion verification require expertise. A mistake produces carbon monoxide. Call a pro if you are not experienced with gas appliance work, if the gas line needs upsizing, or if you are unsure whether your specific model is convertible.
How difficult is this project?
This project is rated advanced. This requires significant plumbing experience. Consider hiring a pro.
How long does this take?
Plan for approximately 2 - 4 hours (professional job). First-timers may need extra time.
How much will this cost?
The estimated cost is $50 - $150 for conversion kit; $200 - $500 professional labor. Costs vary by location and materials chosen.