Written by Amanda Casteel · COO Reviewed by Johnny Casteel · CEO · Master Plumber Updated July 2026 VA Plumbing Lic. 2710075081 · Contractor Lic. 2705180998
Quick answers
- Install and test CO alarms — replace per manufacturer age limits.
- Headache, nausea, or dizziness with gas appliances on → fresh air and emergency services if severe.
- Yellow, lazy burner flames or soot near a gas water heater → shut down and call.
- Orphaned flues after furnace upgrades need professional review — see our chimney/liner education.
When to use this page
When installing or servicing a gas water heater, after a combustion appliance changeout, or when a CO alarm chirps or alarms.
Do this first if an alarm sounds
Get people and pets to fresh air. Call emergency services if anyone is symptomatic. Do not re-enter to “check the heater” until responders say it is safe. Then call us for water heater / plumbing combustion-side follow-up when cleared.
What to have ready for a safety visit
Alarm locations, recent HVAC or water heater work, and whether you smell gas (evacuate for gas smell — that is a different emergency).
What we check on water heater visits
Combustion air awareness, T&P discharge, venting observations we can see as plumbers, and when we hand off to HVAC or specialists for flue/liner issues.
After the crisis
Replace aged alarms, schedule heater service, and read orphaned-flue education if a furnace was replaced without addressing shared vents.
Failure modes to avoid
Silencing a CO alarm without finding the source
Alarms save lives. Treat every alarm as real until proven otherwise by qualified responders.
DIY vent modifications
Improper venting creates CO risk. Licensed pros only.
Proof & methodology
- · Written by Amanda Casteel (COO), reviewed by Johnny Casteel (CEO · Master Plumber) — Cherry Blossom Plumbing (VA Plumbing Lic. 2710075081).
- · Grounded in Northern Virginia / DMV patterns: basement colonials, Arlington rowhouses, HOA townhomes, clay soils, and multi-day storm outages — not invented storm “hero” stats.
Last updated July 2026
FAQs
Do you replace CO alarms?
We focus on plumbing/water heater safety. Alarm installation may be DIY or another trade — we will tell you what we can cover on a visit.
Gas smell vs CO?
Gas smell → leave and call the gas utility / 911. CO is odorless — rely on alarms and symptoms. Both are life-safety first.
Next step
Ready for help in Arlington or Northern Virginia? We diagnose first, explain options in flat-rate terms, and never upsell what you do not need.