CSLB C-36 Plumbing ContractorService, Repair, and MaintenanceMedium
A homeowner reports that their gas water heater is producing hot water, but the flame inside the combustion chamber appears yellow and lazy, and there's a faint soot accumulation on the flue pipe. What is the most likely cause of this issue?
- AExcessive gas pressure entering the burner assembly.
- BA faulty temperature and pressure (T&P) relief valve.
- CA build-up of sediment inside the water heater tank.
- DInsufficient combustion air supply to the burner.
Show answer & explanationAnswer & explanation
Correct answer: D. Insufficient combustion air supply to the burner.
A yellow, lazy flame and soot accumulation are classic indicators of incomplete combustion due to a lack of oxygen. The burner needs adequate air for a clean, blue flame.
Why the other options are wrong
- A. Excessive gas pressure would typically result in a roaring flame, potentially lifting off the burner, and could be dangerous.
- B. A faulty T&P relief valve would cause water to leak or discharge, not affect flame quality or soot.
- C. Sediment build-up reduces heating efficiency and can lead to rumbling noises, but it doesn't directly cause a yellow flame or soot accumulation.
Incomplete Combustion in Gas Appliances
Incomplete combustion occurs when a gas appliance lacks sufficient oxygen to burn fuel efficiently, leading to a yellow/orange flame, soot, and potential carbon monoxide production.
- Characterized by a yellow, lazy flame instead of a sharp blue flame.
- Results in soot accumulation and reduced heating efficiency.
- Can produce dangerous carbon monoxide (CO).
Memory trick: Yellow flame, lazy burn, CO concern.