Do you have a masonry chimney? There should be a clean out on the bottom of the chimney. On a sunny day you should be able to see some light coming in at the top of the chimney. Use a mirror to look up. You can also try using a flash light with a mirror if you are in a hurry.

Related articles to this topic are, 'Checking Water Heater Vent Draft' and 'Blocked Water Heater Vents', follow these links for more information.

Warning!! Shut the Gas Off To Your Water Heater If Your Vent or Chimney is Blocked! The Fumes Can Be Dangerous!!

Can you clean your chimney yourself? Yes, but there is danger involved. You need to take safety precautions before you attempt this. It means getting up on the roof and running a special brush down the chimney. A set of rods and brushes will run between $20 and $50. Don't like being on the roof? A chimney service will run between $75 and $200. You have to do something if your chimney is clogged. For homes with a fireplace, regular chimney maintenance is a must.

You may have a double wall pipe that is used for the chimney. The fittings that lead up to it should be screwed in place. You can remove some of the fittings to get a look up the chimney. Same concept look for daylight or use a flashlight to check for obstructions. If the obstruction is within reach you can use something to clear it out. For an obstruction that is out of reach you will need to call a service.

A blocked water heater vent can be a serious problem. Gas hot water heaters burn fossil fuels that generate, carbon monoxide, a dangerous and deadly gas.

Before you assume that your vent is blocked you want to make sure you check the vent draft. See the article 'Checking Water Heater Vent Draft' for instructions on what to do. Not sure if this is your problem? See 'Repairing Gas Hot Water Heaters' for a listing of all the gas water heater topics.

Any sign of a poor draft may mean an obstruction. There are a couple of things you can do to try and figure out if you have a blockage. Some or all of them may not work in every situation.

Warning!! Shut the Gas Off To Your Water Heater If Your Vent or Chimney is Blocked! The Fumes Can Be Dangerous!!

Locating the Vent

The water heater vent is a section of metal pipe, usually 3" in diameter that runs from the top of the hot water heater to the chimney. It may be connected to a larger metal pipe that also vents the furnace. You only have a vent pipe on a gas water heater, electric water heaters do not need to be vented. This pipe is connected to he chimney located nearby.

Removing the Vent

Before you can check the vent, you need to shut down the water heater. See the article 'Shutting Down a Gas Water Heater' for instructions.

The flue pipe is held together by screws. You can take apart a section by removing the screws that hold it together. Remove enough of the pipe to see the full length of it.  and check for blockages. Make sure the water heater is turned off before you do this.

Have you checked all the pipe that goes from your water heater to the chimney. Did you see a blockage? Remove the blockage using a piece of stiff wire. The vent pipe needs to be completely free of obstructions the full length of the pipe.

If the pipe is clear, you can put everything back together using the same screws that you removed. You do not need any sealer for the fittings on a metal vent pipe. However, the vent pipe should be pitched upward toward the chimney. If it is not pitched properly, you will need to make adjustments. See the article 'Repairing Water Heater Vent Pipes' for more information.

Summary

No blockage, then your problem is else where. See the article 'Blocked Chimney Flues' for more information.

Checking a water heaters vent draft is an important safety concern. The fumes from a hot water heater contain carbon monoxide and can make you sick or even be lethel at certain levels. Making sure that the water heater is venting properly can give you peace of mind. The efficiency of the water heater is also a factor.

Not sure if the vent is your problem?  See the article, 'Troubleshooting a Gas Water Heater' for a complete listing of all the gas water heater topics.

The information below discusses how to check to see if you water heater vent is working properly. There is also some information on how the vent should be installed. If it is not working or not installed correctly, you are going to want to correct the situation.

How a Water Heater Vent Works

The burner is on the bottom of your hot water tank. The burner draws air from the room to burn. In a small room, grilles need to be installed to provide enough air flow. Once the gas is burned it is vented up through the center of the tank to the flue. A properly sized chimney will create a draft that sucks the fumes up and out into the atmosphere.

There is an air space around the fume hood that also allows the heated combustion gases to draw air. The fume hood is held up by short pieces of metal that fit inside of slots on the top of the water heater.

WARNING!! An Improperly Vented Water Heater Can be Dangerous!!! Shut Off the Gas To Your Water Heater WARNING!!!

Checking the Vent Draft

Setting Up the Test

As a rule you should test the vent draft under worst case conditions. What this means is that when other exhausting devices are running, such as a bathroom exhaust fan and there are no open windows, the water heater should still vent properly.

To properly check the vent draft you want to first close all of the windows and doors in the house. You should also close the damper to the fireplace if you have one. Then you want to turn on exhaust fans in the bathroom and kitchen. The dryer should be running also. This may be extreme, but it replicates conditions when everything is being used at the same time.

Turn the furnace down so that it does not run while you are performing the test. Run enough hot water to get the water heater burner to ignite. The burner should run for a few minutes before you perform the test.

Performing a Low Tech Draft Test

When the burner is on for a few minutes you should be able to feel air being drawn into the fume hood. Put your hand next to the vent hood without touching it. Hold your hand sideways and cup it slightly. You should never be able to feel air pushing out of the fume hood. This is called a 'down draft' or 'back draft' and could be serious, see below.

You should be able to feel the air being drawn into the vent hood with your hand. If you can't feel any air being drawn in or you feel pushing back there is a draft problem.

Another low tech way to check the draft would be to hold a match or lighter near the fume hood. The water heater burner should be running for several minutes before you perform this test. The airflow should draw the flame into the hood. If the flame sputters or goes out it could be a sign of trouble. Another thing to look for is soot around the fittings. Any sign of black soot means that the smoke is not going up the chimney.

If there is any evidence that the vent is not working properly, you are going to need to correct the problem. See the articles 'Fixing Blocked Water Heater Vents' and 'Unblocking Chimney Flues' for information on how to remove blockages from the vent and chimney.

Back Draft - What It Means

A back draft as the name implies means that instead of heading toward the chimney air is being pushed back into the room where the water heater is. This is a dangerous condition, since the exhaust from the water heater contains dangerous fumes.

If the test above fails, and you have checked tom make sure there is no blockage, try shutting off one or more of the fans and/or opening a window to see if the draft improves. If it does, you may need to provide some 'make up' air for the water heater. This is usually a duct that provides air from the outside. When the water heater needs additional air, the duct will provide it.

Installing this type of ducting is beyond the scope of this article. There are two pages you can check for more information, 'Water Heater BackDrafting - Part 1' and 'Water Heater Backdrafting - Part 2'.

Checking the Vent Installation

The fume hood should be sitting on the tank level. The vertical legs should be straight and inserted in the slots provided. The fume hood should be directly over the round opening in the top of the hot water heater. If it is crooked or off to one side it should be fixed.

The vent should be pitched upward toward the opening in the chimey. The vent should be pitched at least 1/4" per foot in an upward direction. It should not have an elbow directly above the opening in the water heater. It should not have long horizonal runs. The water heater should be as close as possible to the chimney.

If you vent is not installed in a manner that allows the free flow for the exhaust it will need to be corrected. Reduce if necessary the number and location of the elbows and make sure the ducts are pitched correctly.

Summary

Carbon monoxide is a dangerous gas and extreme caution should be used to make sure it is being vented from the hot water heater. Make sure you don't have any obstructions blocking the ven or chimney flue.

Is a water heater vent an important part of your home. Yes, for more than one reason. Your gas hot water heater needs air to operate. Once the gas is burned the fumes need somewhere to go.

Not sure if this is your problem? See the article on 'How To Troubleshoot Gas Water Heater Problems' for a complete listing of issues and the resources to solve the problems.

The first thing to check would be the 'Draft on the Water Heater Vent'. The next major concern would be 'blockages', 'Blocked Water Heater Vents' and 'Blocked Chimney Flues' cover these issues. Read below for an overview on this subject.

Poor venting can cause your water heater to burn inefficiently. It can also be dangerous, since the burner produces carbon monoxide. What are the problems? Can you fix them yourself? You can learn to solve this problem yourself.

Local building departments have differing requirements for venting a hot water heater and they should be consulted when questions arise. In general the vent pipe that comes up from the hood on the water heater should never be reduced.

You should have as much vertical rise as possible before there is a turn. The vent pipe has to run up hill a minimum of a quarter of an inch per foot. The fume hood needs to be seated properly on the top of the tank. This article deals with water heater vent, repair issues.

Repairing a Water Heater Vent Using Common Sense

For and explanation of the terms in this section, see 'How to Use This Site'.

Troubleshooting Gas Water Heater Vents

How can I check to see if the vent is working?

The first thing you want to know is if your vent is working or not. The article 'Checking the Draft' covered this topic, providing a simple test to see if your vent is drawing properly.

How can I tell if there is a blockage in my flue vent?

A blocked or partially block vent can cause dangerous fumes to build up inside the house. This problem needs to be corrected immediately. See the article on 'Removing Blockages From Vent Pipes' for instructions on what to do.

The vent is clear, but there is still no draft, what is the problem?

Similar to a blocked vent, a blockage in your chimney flue can be dangerous. However, clearing a blockage from the chimney is difficult and requires special tools. See the article 'Clearing a Blocked Chimney Flue' for instructions on what to do.

Summary

So what did you get into? Did you check the draft? You may have had to do some work on your fume hood. They get banged around a little over time. Did you have an obstruction? Were you able to clear it out yourself? Hopefully you have been able to solve your problem. Calling a service to clean out your chimney is an expense, but well worth it.