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Gas Fired Water Heaters Need Proper Venting

Venting of gas fired water heaters is critical because of a process called “combustion”.

Gas fired water heaters utilize either natural gas or propane (LP) gas. The burning of the gas is called combustion. Combustion creates heat, moisture and gas fumes including dangerous carbon monoxide. The venting system directs and safely removes the materials created by combustion into the atmosphere.

The Venting of gas fired water heaters is accomplished via ductwork, which depending upon the type of water heater installed, can be either single duct or dual (concentric) duct made from either metal or PVC.

The proper venting prevents a condition called back-draft. Back-draft occurs when the exhaust created by combustion cannot escape via the ductwork and is forced back into the home. The causes of back-draft include improper installation of venting system or a downward pressure from the atmosphere or even birds or animals building a nest in the ductwork. Most gas fired water heaters now have a safety sensor installed so if back-draft occurs the heater will shut off.

The different types of venting include:

Atmospheric Venting

Atmospheric venting usually consists of a single metal duct that vents from the top of the heater exhaust port directly out the roof. This is most commonly used in homes and small businesses. As combustion heats up the gases, an upward draw is created thru the ducting and vents the gases into the atmosphere.

Power Venting

Power venting water heaters are interesting because you can vent either vertically or horizontally. The heater has a 120-volt fan installed on top of the heater which forces the gases thru the ductwork. The type of ductwork for this venting system can be made of either metal or PVC.

Concentric Pipe Venting

Concentric pipe venting is utilized on direct vent water heaters. The design of the concentric vent, a double wall pipe, is remarkable because the spent gases are directed into the atmosphere by one chamber of the concentric pipe and fresh air from outside is funneled to the water heater for combustion thru the other chamber. The safety benefits of this type of venting are obvious since you are not drawing inside air to feed the heater, thereby greatly reducing the risk of fire.

SAFETY TIP: If your gas fired water heater continually shuts down, please contact a knowledgeable, licensed plumber who can safely and accurately diagnose and solve this issue. Back-draft is a serious and potentially health-threatening issue.

I wish you much success!

“Keeping you in hot water…so you stay out of hot water!”

Doug Wallingford
Wallingford Sales
Water Heater Store