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Gas Water Heater Venting Options – All You Need To Know

The main purpose of the venting system in your gas water heater is to remove flue gases. Whether it is a propane or natural gas water heater, the venting system can effectively remove by-products of combustion. This further helps to draw fresh air.

The flue gases are acidic as they contain carbon dioxide and water vapor. Thankfully, there are different types of gas water heater venting options. You will have to utilize the right type of venting depending upon the gas water heater. It must be reliable, safe, and economical.

Water Heater Vent Types –

1. Atmospheric Vent

The atmospheric vent is the most common type of water heater. It has a vertical metal pipe that is connected to the chimney. These types of vents naturally remove flue gases. It will pass the flue gases from the draft hood to the flue pipe and then to the atmosphere.

The best thing about the atmospheric vent is that it is easy to operate and comes at an affordable value. You can use them without any electricity. Often, efficiency will be higher according to the exhaust gas temperature and longer ducts. However, atmospheric venting systems are vulnerable to backdrafts.

2. Power Vent

One of the best things about power vent water heaters is that you can install them horizontally or vertically. Some of these can have vent pipes of up to 150 ft. It comes with a mechanical fan for taking the byproducts of combustion out. The power vent works by driving the air from the inside by using stainless steel or metal bending pipes.

As condensing units have low temperatures, they can also be used with other materials including PVC. If your home has no chimney, you can opt for a power venting system. However, do note that it is not suitable for installation near the living room. Also, you will need electricity to power the fan. Power vent heaters tend to be expensive.

3. Direct Vent

In a direct vent water heater, you will find a sealed combustion chamber. It uses a horizontal flue pipe for drawing out the flue gases. It uses double-wall vents to draw fresh air. These types of gas water heaters can be perfect for spaces where ventilation is insufficient. They also offer better flexibility during installation.

The main advantage of a direct vent is that it helps in the safe transfer of gases. It comes in a tight design and can operate quietly when compared to power vent heaters. The power vent also does not have any effect on the backdraft. The sealed combustion design lets you install them near corrosive and flammable chemicals.

Gas Hot Water Heater Venting Problems

Gas water heater venting can have different types of problems. However, the most common one is back drafting. Back drafting happens due to the inadequate design of the vent. When it happens, the exhaust gases will move inside the house rather than exiting outside. You will always have to look for back-drafting symptoms like condensation, corrosion at the water heater’s top, and melted plastic at the top.

For a proper draft, you will have to turn off the furnace and close all the doors and windows. Before you test, you will have to start the heater and allow it to run for some time. Confirm if the water heater is back drafting by putting your hand close to the hood. If moisture and warm air are coming out, it means it is back drafting. You can even use a matchstick and check if smoke is pushed away. For a visual indication, you can check the cobwebs.

Water Heater Venting Requirements

For efficient and right ventilation, here are some of the main requirements.

  • Single wall pipes require clearance of 6-inch and cannot pass through walls, ceilings, or floors as long as it is noncombustible. If it is a B-vent chimney pipe, the clearance must be 1 inch.
  • A vent connector is required for vending vertically. However, it must rise 0.25-inch per foot of horizontal run. As there is not much slope, compliance will not be difficult. The horizontal distance must not be above 75% of the vertical distance.
  • The flue of the power vent water heater must not be shared with other appliances.
  • In a draft hood connection, there must be a vertical vent of at least one foot.

As venting systems can have one or two pipes, two-pipe systems further let you separate them into two separate pipes. All the above requisites are important, you will have to confirm with the state and local codes before you apply them.


Gas water heater emits dangerous gases which can be harmful. If not handled properly, it can be fatal. It is important to have proper venting so that there will be a smooth operation. It makes sure there will be safe operation when you have the right type of water heater venting. Without proper venting, there can be many problems, injuries, and incomplete gas combustion.

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