Backdrafting A backdraft is a rapid or explosive burning of superheated gasses in a fire, caused when oxygen rapidly enters an oxygen-depleted environment; for example, when a window or door to an enclosed space is opened or broken. Backdrafts present a serious threat to firefighters. There is some deba…Backdraft
Carbon monoxide
Carbon monoxide is a colorless, odorless, and tasteless flammable gas that is slightly less dense than air. It is toxic to animals that use hemoglobin as an oxygen carrier when encountered in concentrations above about 35 ppm, although it is also produced in normal animal metabolism in lo…
Full Answer
What happens if you Backdraft your water heater?
Backdrafting exhaust gases can condense at the top of the water heater tank. Over time, this corrosive condensate will begin to corrode the top of the tank.
What are the most common water heater draft problems?
Here’s a common scenario for water heater draft problems: an old 80% efficient furnace is replaced with a new, high efficiency furnace that vents through the side of the house, leaving the water heater vent an orphan. The illustration below, provided by the Minnesota Department of Commerce, Division of Energy Resources, shows what this looks like.
What is backdrafting and is it dangerous?
Backdrafting is a potential hazard, but with a little thought and standard maintenance, it’s a danger that can be avoided. Ohio-based freelance writer and author Dan Stout is a former residential remodeler, commercial site supervisor and maintenance manager.
How much pressure is too low to Backdraft a boiler?
Once backdrafting begins and the flue gets cold, it may be sustained for a long time. Research has shown that negative pressure of as little as 5 Pascals (Pa) creates a risk of backdrafting with naturally vented boilers and furnaces.
Why Do Water Heaters Backdraft?
These problems are often found in older houses where the water heater was improperly installed, has lost effectiveness over time, or was replaced with a newer water heater without adapting the venting system. When older furnaces are replaced with newer high-efficiency versions, the old system may not be able to properly vent and needs to be converted or adapted.
How to tell if water heater is back drafting?
There are a variety of ways to see if your water heater may be back drafting. First, look for damage around the tank such as melted seals or rust. Second, check for excess moisture on the tank, pipes, or walls where your water heater is located. Finally, check the pitch of your vent connector, which should pitch upward with at least ...
Can a water heater cause mold?
However, older or improperly installed water heaters can cause serious problems spilling toxic carbon monoxide and excess moisture (which can cause mold and mildew) into your house.
How to tell if a water heater is backdrafting?
Another easy way to get visual evidence of a backdrafting water heater is to hold a camera close enough to the draft hood to allow the lens to get fogged up from the backdrafting flue gases. Powerful stuff, huh?
What is backdrafting in a water heater?
Backdrafting at a water heater is a common defect identified during home inspections, and it’s almost always a condition that the homeowner or occupant is not aware of. This happens when the exhaust gases from an atmospherically vented water heater spill out into the room, rather than safely leaving the house through the vent.
What is a marginal or improper installation of the vent connector?
A marginal or improper installation of the vent connector. The vent connector at a water heater needs to pitch upwards towards the vent, and should ideally not have any quick turns, especially right at the draft hood. If you find these types of clues, there might be a problem with the water heater drafting properly.
How to get a water heater to kick on?
Close any fireplace dampers, if present. Turn on any kitchen and bathroom exhaust fans. Turn on the clothes dryer. Run hot water at a bath tub or laundry sink long enough to get the water heater to kick on.
What causes corrosion in water heaters?
Corrosion at the top of the tank. Backdrafting exhaust gases can condense at the top of the water heater tank. Over time, this corrosive condensate will begin to corrode the top of the tank. A leaking shutoff valve can also cause corrosion at the top of the tank, but that type of corrosion is easily distinguishable back corrosion caused by ...
Can backdrafting water heaters cause condensation?
Excessive condensate on the cold water pipes in the water heater room. After a water heater has backdrafted for a while inside of a utility room, there will probably be heavy condensation on the cold water pipes. It’s typical to see condensation on cold water pipes during the summer, but a backdrafting water heater will make it dramatically worse.
Can a water heater draft if the window is closed?
A few days ago, by chance, I noticed that the heater was firing, but the flue was dead-cold… After some observation and experimentation, I can conclude that, in weather conditions colder when our usual mild Mid-Atlantic winter and with all doors windows closed, water heater is not able to establish the draft. If a window is opened for a few seconds, then it starts drafting fine and continues to do so even after the window is closed.
What is backdrafting in a home?
Backdrafting is a dangerous situation where toxic combustion gases are not properly vented. Instead of rising up through a chimney and releasing outside, some exhaust gas enters the home. Backdrafting is primarily a concern with atmospheric venting gas water heaters.
How to know if water heater is hot?
Cup your hands around the draft hood (the cone-shaped vertical pipe at the top of your water heater) and see if you feel warm, moist air
How to fix a water heater that is leaking gas?
The most immediate thing you can do is improve the ventilation in your home by opening the windows or running a nearby exhaust fan, such as in a bathroom or kitchen. Next, call an experienced HVAC technician to look at your water heater and see what can be done. It may be possible to correct the ventilation setup, replace a missing vent cap, or install a power vent.
Why is there water on the top of my water heater?
Look for corrosive stains on the top of the water heater, which would be caused by condensate from the exhaust; likewise, if you see water/moisture on top of the tank, this could be from backdrafting
Can a water heater vent go out of the chimney?
With an atmospheric venting water heater, hot exhaust gases are designed to naturally rise and go out of the chimney. If the vent was installed incorrectly, such as the vent pipe having too many angles or a downward slope, the exhaust gas will not reach the top of the chimney on its own. Furthermore, if there’s a blockage in the vent, this could force the exhaust gases down the pipe and into the home.
Is it time for a new, safer water heater?
Atmospheric gas water heaters are usually entry-level units. A safer choice may be a power venting water heater with a fan that helps push the combustion gases out of the home, instead of relying on the natural rise of the gases. This type of venting greatly reduced the chance of backdrafting.
Why does my water heater back draft?
The main reasons for backdrafting at the water heater are the poor vent installation and obstructions found in the vent pipe.
Why does backdrafting cause corrosion?
Backdrafting can also result in metal corrosion because the condensate, which is acidic by nature, can appear on the top of the heater, where hot gases get in touch with the cold metal elements. If playback doesn't begin shortly, try restarting your device.
What is the gas in a water heater?
The exhaust gases contain poisonous gases such as carbon monoxide, moisture that is acidic and can produce corrosion on the metal parts. Every atmospheric vent gas water heater is equipped with the draft hood found at the top of each unit, where the venting pipe is attaching to the water heater. Also, this is the place where backdrafting can be ...
How to check for backdrafting?
The simplest way to check for backdrafting is to put hands around the draft hood, mirror or glass. You will feel the warm gases coming out while the moist inside the flue gases will make the mirror/glass fog up if used as the checking tool. You can also use the lighter or matchstick beside the draft diverter, and if there is sufficient draft inside ...
How to tell if a draft hood is backdrafting?
If it was backdrafting for a long time… check the elements surrounding the draft hood; you might see some dark residues, also known as soot. Look for the plastic caps on the incoming cold and outgoing hot water pipes. As said, exhaust gases have a high temperature, and if they leak under the draft hood, the plastic elements can be affected - they can change the shape, discolor or melt.
How many openings should a water heater have?
The room where the water heater is located should have two openings, upper and lower, and the size should be done per manufacturer’s instructions, so the outside air can freely enter the room and in a sufficient amount.
Do you need to install a vent cap on a flue vent?
In order to prevent the foreign body from getting into the flue vents, it is recommended to install the vent cap, no matter if the vent termination horizontal or vertical.
What does it mean when a water heater backdrafts?
If a water heater backdrafts, it means that potentially hazardous exhaust gases are coming back into the home. Last week I blogged about how to determine if a water heater is backdrafting; that’s the easy part. The tough part is determining why it’s happening and fixing it. There are many potential causes for a water heater to backdraft, ...
How to make a water heater draft?
For a water heater to draft properly, it needs to have plenty of available air. Some water heaters will be right on the brink of backdrafting even with a proper installation, and all it takes is a single bathroom exhaust fan to pull enough air out of the house to make the water heater backdraft. Even in a home with a water heater that drafts very well, just throw in a big 600 cfm kitchen hood fan and it’s almost a guarantee that the water heater will backdraft with the fan running.
Why is my water heater venting back?
The relatively small burner on the water heater may not generate enough heat to warm up the chimney or vent, which can lead to backdrafting. In many cases, a new vent liner will be installed to allow the water heater to vent into a smaller space.
What is the difference between a short and tall water heater?
Most atmospherically vented water heaters come in two shapes – tall and short. Short water heaters are a couple of inches wider and nearly a foot shorter than tall water heaters.
Can a water heater be moved closer to the chimney?
That water heater could certainly be moved closer to the chimney. Another thing that can be done to help with a long horizontal run is to replace a single-wall vent connector with a Type B vent connector. This will help the vent to heat up faster, which will help with draft.
Can a chimney vent cause backdrafting?
An obstructed chimney or vent will almost certainly cause backdrafting. I’ve heard stories of leaves, acorns, and squirrels in chimneys and vents; I once even found a dead bird blocking the draft hood at a water heater. To help prevent the possibility of that happening, a listed cap should be installed at the vent terminal at the exterior.
How to prevent backdrafting?
There are three key elements to preventing backdrafting: 1 Heating equipment maintenance to avoid backdrafting: In existing equipment, make sure all burners are properly adjusted and that flues are properly sized and free of cracks or blockages. Inspect annually. Common Indoor Pollutants and Sources 295 2 Heating equipment venting to avoid backdrafting: In new construction, eliminate all atmospherically vented appliances, including woodstoves and fireplaces. 3 Building Depressurization causing backdrafting: Minimize depressurization by reducing exhaust fan sizes and balancing airflows in heating, cooling, and ventilation systems.#N#See COMBUSTION AIR for TIGHT BUILDINGS for details on how to provide adequate combustion air in tight buildings.
What is backdrafting in HVAC?
Definition of backdrafting: Back-drafting or feeding of combustion products out of the burner area into the building's occupied space air occurs when a gas or oil fired heating furnace draws air out of the exhaust flue (or out of a leaky heat exchanger) and sends it into the HVAC duct system.
What happens if a gas log fireplace is not vented?
If the gas-log fireplace shown at left is not properly vented, spillage of combustion gases including possibly carbon monoxide into the building interior may be continuous. In tight quarters there is also the risk of oxygen depletion. Watch out: Both of these are potentially fatal hazards.
What is it called when a flue gas spills into the house?
When the flow reversal lasts for 30 seconds to a minute, it is called spillage ; longer sustained spills are called backdrafting, a far more serious condition.
Why is my chimney not drawing properly?
A chimney or flue that is too large, too small, or blocked by a bird’s nest or loose brick will not draw properly and will be prone to spillage problems. Uninsulated chimneys on outside walls are also prone to poor draft and to condensation problems that can deteriorate flue materials. These problems should be fixed first before addressing problems inside the house.
How many CFm can a bathroom fan draw?
To keep indoor depressurization to a minimum, do not oversize bathroom and kitchen fans, and avoid the use of downdraft and island fans, which can draw 600 cfm or more. If large fans must be used, they should be interlocked with a supply fan to provide makeup air.
How much pressure can a power vented air conditioner handle?
These draw their makeup air from indoors and are also called fan-assisted, forced-draft, or mechanical-draft. These can typically tolerate up to 15 to 20 Pa of negative pressure.
