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Gas Water Heaters
Water Heater Gas Valve Problems
Working on a hot water heater gas valve is not a repair for your average homeowner. Replacing is is generally the only option.
There are several things you want to check before you assume your gas valve is bad. Make sure you rule out simpler repairs first. See the articles 'Hot Water Heater Pilot Litght', "Hot Water Heater Thermocouple', before you plan on replacing your gas valve.
See the article 'Gas Hot Water Heater Troubleshooting', if you are unsure of your problem.
How a Gas Valve Works
The gas valve sends gas to both the pilot light and the main burner. It senses electrical current from the thermocouple and shuts off the gas if the pilot is not lit. This is an important safety feature. There are not a lot of options if the gas valve is bad.
Replacing it is usually the only course of action. This is a bigger repair job and the part it fairly expensive. However, you would only look at the water heater gas valve after you have checked the thermocouple. The symptoms are the same.
Water Heater Gas Valve - The Issues
What Can You Save? - This is not a cheap repair. The part alone could run $80 to $250. The high end is brand named part vs. an after market replacement. There is a fair amount of labor. This could run you another $200 to $250. Then there is the 'why spend that much on an old water heater' pitch. You could get talked into an new water heater. Anywhere from $800 to $3,500.
How Hard Could It Be? - Replacing a water heater gas valve involves draining down the tank, unhooking the gas line, unhooking thermocouple and gas lines to the burner and actually changing the valve. A couple of hours of break a sweat work. These repairs will have a Difficulty Level of: A Bit of Work. These repairs require a Skill Level of: Determined Handyman. For and explanation of the terms in this section, see 'How to Use This Site'.
What Can Go Wrong? - You are dealing with natural gas. Make sure the gas is turned off and the area is well ventilated. There will be some residual gas in the lines when you take them apart. Also the water in your tank is hot, shut the tank off and run some hot water until it is lukewarm before you try to drain it. Not getting it fixed will leave you without hot water. This will likely generate a significant amount of complaining from the family.
Gas Valve Thermostats
The gas water heater thermostat is part of the gas valve. The thermostat cannot be replaced independently from the gas valve. In addition, there is no practical way to test it. You can replace the gas valve, although, unless your water heater is not working at all this should not be needed.
Are you convinced that the thermostat is not working properly? You could test the temperature of the water coming out of the tank. The reccommended temperature is 120 degrees.
You can make adjustments to compensate, if you find that the temperature is too low. Be very careful about raising the temperature above 120 degrees. Burns and scalding can occur. See the article 'Gas Water Heater Temperature Settings' for more information.
Take a look at the article 'Water Heater Gas Valve', if you think your gas valve has gone bad. Another thing you should check is the 'Gas Water Heater Thermocouple', this is the more likely candidate for issues with your gas valve. The gas valve will not work properly when the thermocouple is defective.
Purchasing a Gas Valve
Before you can replace your water heater gas valve, you need to purchase a new one. You may find that getting an exact match to the one you have difficult.
Shutting Off the Gas
The first thing you need to do is shut off the gas to the hot water tank. This is done at the shut off valve that is in the gas line.
Turning the water heater gas valve to off is not the place to do this. The 'Off' position on the gas valve dial only means that it will not heat the water. The pilot light is still on and gas from the main supply line is still on.
You need to turn the inline valve ninety degrees so that it is perpendicular with the gas line.
Cooling off the Hot Water
Next you want to run some hot water into a sink until the water cools down to lukewarm. The water in your tank can be very hot and dangerous. Cooling it off will make the draining operation a lot safer.
Remember, no repair project is worth getting hurt over. You can get some information on Safety if you click that button on the sidebar.
WARNING!! Natural Gas Can Explode! Make Sure the Gas is OFF!!! Hot Water Can Cause Severe Burns!!! WARNING!!!
Draining the Tank
Shut off the water supply at the cold water inlet for the water heater. Next, hook up a garden hose to the water heater drain valve. Find a drain to run the garden hose to and make sure the hose will stay secure. Open the valve to allow the water to start draining. Open the pressure relief valve to allow air to get into the tank.
Does your tank have a sediment build up in it? This might be a good time to flush the tank. Go to the article Flushing a Hot Water Tank for instructions on what to do. You will have some wait time while the tank is draining. See Step Three for work you can get done in the mean time.
Unhooking the Lines
You will normally have four items that are hooked to the water heater gas valve. (1) The Gas Line (2) The Thermocouple (3) The Pilot Light Supply Line (4) The Main Burner Supply Line. A possible fifth item would be an electronic igniter that is attached to the side of the gas valve.
(1) For the Gas Line, you should find a union between the shut off valve and the gas valve. Loosen the union using two pipe wrenches. The gas line has a horizontal pipe that feed into the side. The other end is connected to a tee. You may have to take off the nipples on either side of the tee to be able to remove the nipple going into the water heater gas valve. Remove the gas line from the gas valve. Save the pieces, you will need them.
(2) Use an open end wrench or an adjustable wrench to remove the thermocouple. Be careful, some of them have left handed threads. If it won't loosen going the normal way, try the opposite direction.
(3) Next use an open end wrench or an adjustable wrench to remove the supply line for the pilot light. It will be the smaller of the two and likely on the far right.
(4) Use the proper size open end wrench or an adjustable wrench to remove the supply line to the main burner. This will be the larger line in the center of the gas valve.
(5) The igniter if you have one is not really a component of the gas valve. However, it may be attached to the side of it via a bracket. Use a screwdriver or nut driver to remove it as required.
Replacing the Gas Valve
Step Four – Replacing the Gas Valve
Removing the Gas Valve
You need a small pipe wrench to remove the gas valve. Make sure the tank has finished draining. The gas valve stands away from the tank housing. You likely have only 3/4" of space to work in. The jaws of the pipe wrench need to be about 5/8" wide. As you face the water heater, turn the gas valve counterclockwise to remove it.
You need to get a suitable gas valve replacement. There are a number of universal models available. There should be a model number on the side of your old gas valve. You can try searching for that model number to see if you can find an exact match. Your success will depend in part on the age of your water heater. For a universal one, the shank length is the main concern. They come in various lengths from 1 1/4" to 2 3/8". Make sure the one you get has the same shank length.
You want to put some pipe joint compound or Teflon tape on the threaded portion of the pipe that goes to the hot water heater. Use the pipe wrench to tighten the valve. Make sure it is tight. You should finish with the pilot knob facing up.
Filling the Tank
At this point you are ready to fill the tank. Close the drain valve and turn on the water supply. You want to make sure that there are no leaks around the gas valve.
When you start to get some water out of the drain for the pressure relief valve, you can close it. Open the a hot water faucet nearby and let it run until all of the air is bled out of the tank.
You will need to tighten the gas valve if the water is leaking. You will probably have to go a full turn to get the valve turned the right way.
Putting the Water Heater Back Together
You can re-install the lines coming into the bottom of the water heater gas valve in reverse order of taking them off. These fittings should not need any pipe dope or Teflon tape. Make sure the connections are tight. You will need to use a pipe joint compound on the gas line fittings that is rated for natural gas or one that is approved by your local building codes. Use pipe wrenches to put the gas line back together. Make sure you tighten the union.
Make sure the dial on the water heater gas valve is set to off. Turn the shut off valve on the gas line to the on position (parallel with the gas line). Use soapy water to check for leaks. Never use a lighter or any kind of flame to check for gas leaks.
After you are confident there are no gas leaks you can go through the pilot lighting procedure. You should have gotten some instructions with your new water heater gas valve. After the pilot is lit you can turn the valve to on and set the temperature. It should be set at the factory for 120 degrees. At this point you should use soapy water and check the fittings on the bottom of the water heater gas valve for leaks. Be careful about exceeding that, especially if you have children or anyone else that might inadvertently turn on just the hot water.
Put the instructions for pilot lighting you got with the new valve in a plastic bag. Tape it to the side of the water heater. Pilot lighting procedures differ slightly for valve to valve. You will want this information later.
Hot Water Heater Gas Valve Replacement Summary
Is it working now? That is great news. Was that a hard job? Yes it was kind of difficult. Draining the tank is a job in itself. Then removing the lines into the gas valve. You probably had to take at least a couple of the pipes for the gas line apart. Changing the gas valve and then putting it back together. At least two hours on a good run.
Now that you have that behind you, what are you going to do? Ambitious? Want to tackle something else? Tired? Why not take a breather before you get into another project.
Blocked Chimney Flues
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.
Checking Water Heater Vent Draft
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.
Blocked Water Heater Vents
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.
Gas Water Heater Vent Repair
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
What Can You Save? - Checking and cleaning your vent will run you between $75 and $125. There is not much to it. A repairman should have a meter that checks the draft. Other than that it is pretty simple. Having your chimney cleaned could run another $75 to $200. Chimney cleaning is needed if there is an obstruction.
How Hard Could It Be? - Cleaning and checking a water heater vent is not that hard. These repairs will have a Difficulty Level of: Simple. These repairs require a Skill Level of: Handyman
For and explanation of the terms in this section, see 'How to Use This Site'.
What Can Go Wrong? - There is a serious danger that can arise from an improperly vented water tank. Carbon monoxide can be deadly. Make sure you have a working carbon monoxide sensor in your home. Shut the hot water tank down if you suspect the vent is blocked. Clear away the obstruction first. Shutting the hot water tank down could be a big inconvenience.
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.