No Hot Water — DIY Water Heater Troubleshooting & Repair
Problems with no hot water? Quickly diagnose and repair your water heater problem with this comprehensive troubleshooting guide. Videos, drawings, and easy to understand step-by-step DIY advice show you how to fix your water heater.
This article will show you how to troubleshoot and fix both gas and electric storage water heater problems. If you have a tankless water heater that is not working, please see Tankless Water Heater Repairs.
How to Tell If Your Water Heater Is Gas or Electric
Here is advice for homeowners who aren’t sure which type of water heater they have.
To quickly tell the difference, look for a flue. A combustion appliance that burns fuel such as gas must vent the exhaust fumes to the outdoors through a flue (a round chimney pipe). A flue indicates that the water heater burns gas or another combustion fuel, such as propane.
In addition, a gas water heater has a gas pipe going to it, a pilot light, and a burner at the bottom of the hot water tank. The burner is typically behind a small metal access panel or viewing door. If you look past the access panel or viewing door, you should see a flame unless the pilot light is out.
An electric water heater doesn’t produce combustion gasses, so it doesn’t have a flue at the top. It does, however, have an electrical cable or conduit that connects it to an electrical panel. It has one or two thermostats on the side of the tank.
No Hot Water Anywhere In the House
No hot water throughout the house is by far the most common water heater complaint. This usually indicates that the water heater’s gas burner or electric heating elements are not producing heat.
To be sure your entire house is without hot water, check every hot water faucet and fixture. If you find one or more fixtures have hot water, skip to Hot Water Not Working In Part of The House.
Also check other gas appliances in the house—such as a gas range or furnace—to see whether they work. If they don’t, your home’s gas supply has been interrupted—call the gas company.
Next, touch the water heater’s temperature-pressure (TP) relief valve and the hot water outlet pipe above the water heater (see water heater diagrams above).
If you feel warmth, your water heater is probably working. The hot water may be getting blocked somewhere in the pipes between the water heater and the fixtures. Of course, the TP valve or pipe could still be warm if the water heater stopped working within the last 3 or 4 hours because the water inside would still be holding some heat.
If the TP valve or outlet pipe is cold, the water heater hasn’t been working for several hours. If this is the case and hot water is not available at any fixture, do the following.
Because methods for repairing the problem may depend on whether your water heater is gas or electric, these are discussed separately below.
No Hot Water — Gas Water Heater
If a gas water heater isn’t heating, a common problem is usually that the pilot light has gone out. This may be caused by the gas valve, the natural gas supply, or—more likely—the thermocouple located next to the pilot light.
The following training video for water heater service people is excellent for gas water heater troubleshooting. Skip forward to the 11:15 mark in the video if you want to jump to dealing with no hot water.
First, look inside the inspection window at the bottom of the water heater tank for a small flame: the pilot light. In some cases, this may look like a small LED light. In fact, it may be so small that you’ll need to dim the room lights to see it.
If the pilot light is out, follow the instructions posted on the water heater or the details below here to relight the pilot light.
The first thing to check on a propane water heater is the gas level in the propane tank outside. If it’s low, have it refilled.
In the following video, you can see that the most frequent cause of no hot water in a gas water heater is that the pilot light has gone out. This can happen if the natural gas supply is interrupted, the gas valve is turned off, or a gust of wind blows out the pilot light.
This video guides you through the process of relighting a typical water heater’s pilot light. The good thing about this video is that the service person is working on an actual water heater rather than a disassembled model like the one in the video above.
How to Relight a Gas Water Heater Pilot Light
The problem is often that the pilot light has gone out. This can be caused by the gas supply being interrupted, the gas valve being turned off, or a gust of wind blowing out the pilot flame. Look for a very small flame—the pilot light—through the viewing window at the bottom of the water heater. If you don’t see a pilot light, try relighting the pilot. Instructions are almost always posted on the water heater, but these generic directions work for most water heaters:
1. Turn off the water heater’s gas shut-off valve.
2. Wait 5 minutes for gas to clear from the water heater.
3. Open the access cover to the pilot light (under the gas valve).
4. Turn the gas valve to “Pilot.”
5. Push down the knob (or a separate pilot button) to start the flow of gas to the pilot. Continue holding it down.
6. Use a long lighter to reach into the access and light the pilot. Keep holding the button down.
7. After holding down the knob or button for about one minute, slowly release it. Make sure the pilot flame stays lit.
8. Turn the water heater’s gas valve to “On.” When you do this, you may hear the burner ignite.
9. Secure the access cover back in place.
To relight the pilot light of a water heater like the one shown in the above video:
- Hold down the pilot switch and click the ignitor button repeatedly. A tiny spark should ignite the pilot when you click the ignitor.
- When the pilot ignites, continue holding down the pilot switch for one minute. During this minute, the pilot flame heats the thermocouple or thermopile. This device, when heated, provides the tiny amount of electricity needed to operate the water heater gas valve.
- After one minute, slowly release the pilot switch and make sure the pilot light stays lit. If it doesn’t stay lit, repeat the process.
If the Water Heater Pilot Light Won’t Light
If you the pilot flame won’t light when you click the ignitor, look to verify that a tiny spark is happening by the pilot. If necessary, dim the room lights. If there is a spark, gas isn’t reaching the pilot. The cause may be:
• Air in the gas line. If the water heater was newly installed, the gas line is probably full of air. You’ll need to purge this air from the line by holding down the pilot knob longer.
• The gas valve on the gas supply pipe may be turned off. Be sure it is open. The valve handle should be parallel to the pipe.
• The thermocouple may be defective. See more How to Replace a Water Heater Thermocouple below. Call a water heater repair person if you don’t have the tools or skills to handle this.
• Low gas pressure or a malfunctioning gas control valve could also cause a pilot light to go out repeatedly. Call your gas company or a water heater repair person if you suspect this is the case.
If the Pilot Flame Keeps Going Out
If the pilot flame lights but keeps going out, its orifice could be dirty and clogged, making the flame small and unsustainable. Check to make sure there is no obvious dirt and debris clogging it.
If the pilot light goes out after you light it, click the high-limit reset switch (sometimes called a door switch), located down by the viewing door at the bottom of the water tank. Please refer to the video at the top of this article and advance to the 18:30 point in it to see a detail of how to reset this switch. Just push the button of this switch and listen for a click.
Then try relighting the pilot again.
If it still doesn’t stay lit, the problem is almost always a defective thermocouple. This is an inexpensive part—about $20. Professional installation, which we recommend unless you are an experienced do-it-yourselfer, should cost about $150, part included. Instructions for replacing it are in the video below.
Water Heater Burner Troubleshooting
If the pilot stays lit, as it should when working properly, turn the gas valve to ON. The burner should ignite.
If the burner ignites, turn the thermostat back to an appropriate heat setting. Your hot water heater should work now.
If the burner does not go on, set the thermostat at about 120 degrees F. and turn on a hot water faucet. Wait a few minutes to see if the water heater burner ignites. If it doesn’t ignite, leave the hot water running and try lowering and then raising the temperature setting on the dial until the burner ignites.
If the burner still doesn’t ignite, turn off the hot water and read on. The water heater’s gas valve and thermostat may be defective.
Gas leaks. If you smell gas near it—the smell of rotten eggs or a garlic-like scent—turn the gas valve control to OFF (you may have to push down to turn it). That is the smell of natural gas. Wait until the gas smell has dissipated before relighting the pilot light.
Water Heater Gas Valve Troubleshooting
Two main types of water heater gas valves are commonly used on storage water heaters: mechanical and electronic. These two valves are thoroughly discussed in the following video and the video at the top of this article.
If you’re a service professional or an avid do-it-yourselfer, and you want to understand the differences between classic mechanical gas valves and a newer electronic gas valve, watch the video here. It also discusses how to diagnose and handle problems.
Mechanical gas valve. Repair people speak highly of classic mechanical-style gas valves because they have served tried and true for decades. You can replace a simple part such as the thermocouple without replacing a major component.
Electronic gas valve. Many newer water heaters use a new electronic control valve called the Honeywell Smart Controller. Helpful for diagnostics, it has blinking lights that inform you or the service person about the water heater’s status.
As you might expect, this controller is more expensive than a mechanical gas valve, as are its replacement parts. Replacement of this may cost $300 to $400, installed.
No Hot Water — Electric Water Heater
When an electric water heater doesn’t heat water, either the power to the water heater has been interrupted or the controls or heating elements are not working.
Always shut off the power to an electric water heater before working on it. And never work on it if water is pooled on the floor near the appliance. Shut off the circuit to the water heater at the circuit break box and call a qualified water heater repair person.
Perform these diagnostics:
1. Be sure electricity is being delivered to the appliance. Check the main switch on the water heater and the circuit breaker (or fuse) that serves the water heater.
If the circuit breaker has tripped, reset the circuit breaker by flipping it all the way to OFF and then back to ON.
If a fuse has blown, replace it with a new fuse with the same rating. If the circuit breaker or fuse repeatedly blows out, call a qualified electrician to check and repair the circuit. Note that the water heater should not share a circuit with another appliance—it draws too much power when heating.
2. Check the high-temperature cutoff on the water heater. Open the panel and look for a reset button. Push it. If the button doesn’t make a clicking sound or you still don’t have power after pressing it, then your high-temperature cutoff switch is probably bad. Call an electric water heater repair person.
3. If there is any water inside the compartment, this could cause the thermostat to malfunction. Leaking water means that your water heater may need to be replaced. See Water Heater Is Leaking.
If these steps don’t solve the problem, one or both heating elements may be the problem. You can replace these yourself following the manufacturer’s instructions, or call a water heater service professional. See the following video for additional help.
Electric Water Heater Troubleshooting
This video does a good job of illustrating how to make sure electrical current is flowing to the electric water heater. Similar to the video directly above, it also shows how to test the thermostat and elements, but it does a particularly good job of showing details such as the exact screws and terminals to test with a multimeter and how to use the multimeter.
Hot Water Not Working In Part of The House
Unless you have two or more water heaters, hot water in some part of your house means that the water heater is working. But something is keeping the hot water from traveling to the faucets or fixtures that don’t work. A typical example of this would be that the kitchen faucet produces hot water but you can’t get a hot shower.
Common reasons are:
• A cross connection. If you’re getting full pressure on the hot water side of your faucets but no hot water, then the problem probably isn’t a valve or a blockage. In that case, there may be a cross connection in the plumbing.
A cross connection can occur in a failing shower valve (or any mixing valve) that allows cold water to pass to the hot side, letting cold water into the hot water pipe. Or it can happen if a plumber makes a mistake when installing pipes.
• A closed valve. If there is a valve on the hot water pipe that exits the tank and goes to the non-working fixtures, be sure it’s all the way open.
• Mineral deposits in the pipes. If old steel water pipes have never been replaced, they may be filled with deposits that restrict water flow. Or chunks of mineral deposits may have broken loose from pipes or the interior of the water heater and traveled through the pipes to a place where they lodge (such as at an elbow), blocking water flow.
• Ice, if the pipes have frozen recently. Frozen pipes can restrict flow to part of the house. See How to Repair Frozen Water Pipes. Of course, if the weather isn’t freezing, this isn’t the problem.
• Distance. If the water heater is far from the fixtures that aren’t getting hot water, the pipes from the water heater may go through an unheated space such as a basement or attic where they give off their heat. Once the pipes warm up, this shouldn’t be a problem.
Answers to this issue are turning up the heat dial on the water heater, insulating the hot water pipes, moving the water heater, installing a second water heater or adding a recirculating pump system. Foam pipe insulation minimizes heat loss through hot-water pipes. If you can gain access to your hot-water pipes, from the basement, for example, put foam water pipe insulation sleeves onto them.
• A water recirculating pump system. If you have one of these, a defective check valve could allow cold water into the hot water pipe.
No Hot Water In An Apartment
One of the downsides of apartment living is that you’re not necessarily in control of your own water heater. In addition, your neighbors’ usage can affect your supply of hot water if you share a water heater.
Your first step should be to contact your landlord and alert them to the problem. Even though it may not be specified by your lease, your landlord is responsible for providing a healthy, safe space. Hot water is considered essential to healthy living. Documenting your complaint in writing is a good idea.
Someone will need to find out whether or not your unit is the only one with hot water problems. If it is the only one, a plumber should be dispatched to check your plumbing. If not, building-wide pipes and water heaters will need to be fixed.
The issues that may be restricting your hot water are all the same as those discussed above. With that in mind, the repairs will be the same.
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