Can a Water Heater Leak Carbon Monoxide?
What this costs
| Option | Job | Low | High |
|---|---|---|---|
| Replace | Water Heater Replacement | $680 | $1,900 |
How it happens
Gas water heaters burn fuel and send exhaust out a vent. CPSC says to keep vents clear and check chimneys and flues for blockages, corrosion and disconnections. Rheem lists common venting mistakes on gas units, including the wrong pipe size, too little upward slope, loose or disconnected sections, and skipping a draft check. We recommend a licensed plumber or HVAC technician to fix these. We don't give steps.
Signs to take seriously
You can't rely on your nose. CPSC says CO is odorless and colorless. Fuel gas has an added smell, so a gas smell and carbon monoxide are different problems. Any gas smell means leave first, too.
- A CO alarm sounding. Treat it as real.
- Headache, nausea or flu-like symptoms without a fever, which CPSC names as early signs.
- More people feeling ill at home and feeling better when they leave. That pattern is our own caution, and it's worth a call.
What to do
If an alarm sounds or you suspect CO, CPSC says to leave for fresh air and call emergency services. Don't go back until responders say it's safe. We recommend having a licensed technician check the water heater and vent before you use it again.
How to protect your home
USFA says to put CO alarms in a central spot outside each sleeping area and on every level. CPSC covers placement, testing and replacement too. CPSC says inspectors should check chimneys and flues for blockages, corrosion and disconnections, so we recommend calling a licensed technician if you see any of those, or after a new heater goes in.
Water Heater Leaking? What to Do Right Now
Common questions
Can an electric water heater make carbon monoxide?
Will I smell it?
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Last verified 2026-11-04
- U.S. Consumer Product Safety Commission: Carbon monoxide fact sheet — Water heaters among fuel-burning appliances that can malfunction and produce CO; vents; symptoms; alarm response.
- U.S. Fire Administration: Carbon monoxide — Alarm placement outside sleeping areas and on every level; keep vents clear.
- Rheem: Top installation mistakes plumbers see with water heaters — Gas venting mistakes: wrong-size pipe, poor pitch, loose or disconnected sections, skipped draft check.
- Public Service Commission of Wisconsin: Natural gas consumer safety — If you smell gas, leave immediately and call the gas utility's emergency number or 911 from a safe distance outdoors; odor described as rotten eggs, sulfur or garlic.
General information, not professional advice. Conditions, codes and prices vary. Turn off power, gas or water before any work, and hire a licensed professional when in doubt. Cost figures are our estimates, not quotes.