The geyser flue and conical baffle: venting and heating

What each part does

• Flue tube: runs up through the tank; the hot gases heat the water through its walls.
• Baffle: a conical or spiral metal strip inside the flue that creates turbulence and slows the gases.
• Flue pipe and cap: carry fumes outside and keep rain and wind out.

Common problems

• Missing or rusted-away baffle: water heats slowly and more gas is used.
• Soot build-up: reduces draught and heat transfer.
• Missing cap: rain rusts the burner; wind blows the pilot out.
• Blocked or disconnected flue: fumes spill out, a serious carbon monoxide risk.

Safety

Never block the flue or run a gas geyser with a disconnected flue pipe, and never install one in a closed room without venting to the outside. If you see soot around the top of the geyser or smell fumes, switch it off and get it checked.

Wind and the pilot

A good flue cap is the first defence against wind blowing out the pilot. For exposed rooftop geysers, automatic ignition then covers the times a gust still gets through.