Water heater pilot lit but no hot water

Ice cold showers are anything but pleasant, so if you can’t get any warm water, you’ll want to get to the solution quickly. However, if your water heater won't turn on even though your pilot light is on, this could leave you scratching your head. This problem could come down to a few different issues, including an old or broken thermostat or sediment accumulation. 

What Causes Water Heater Issues Even When the Pilot Light Is On?

There’s nothing better than a hot bubble bath after a long day. But when your water heater is malfunctioning, it can put an icy-cold wrench in your plans. 

The four common causes of discrepancies between the pilot light and heater are:

  • Drift

  • Sediment

  • Rust

  • Malfunctioning thermocouple

Let's cover how to diagnose a water-heater burner that won't turn on to avoid a water heater catastrophe at your home.

1. Assess Your Heater

Water heater pilot lit but no hot water

Photo: BanksPhotos / iStock / Getty Images

Start with a visual assessment. If you think that the burner isn't on because you can't hear the familiar sound, remove your cover plate to confirm that you can't see the burner firing.

Once you confirm that you're not getting a light, move to your temperature dial. Here's how you want to troubleshoot:

  • Turn the dial to "vacation" or "low"

  • Go back up to your desired temperature

  • Check for a light

But what if that doesn't do the trick?

Let's bring it up a notch. This time, start by switching to "vacation" or "low" mode. The difference is that you're now going to go up 10 degrees to 20 degrees higher than your desired temperature. You might just see the light kick on.

This trick often works because thermostats will lose accuracy through something called "drifting" as they get older. Just make sure you're not letting your water get too hot when you use this trick. Faucet temperatures of 120 to 140 degrees Fahrenheit are considered safe for avoiding scalding. If you have children or elderly family members living in your home, scale that down to 120.

2. Check for Sediment Accumulation

If the dial trick doesn't work, you could have a sediment issue. Sediment accumulation at the bottom of a tank can easily cause your thermostat to malfunction. The sediment buildup will act as insulation that causes your thermostat to reach the indicated temperature before your water does.

This accumulation is a common cause behind warm water that never fully heats up. Signs of sediment accumulation include popping or banging noises, as well as dirty-looking or bad-smelling water. If you see any of these signs, it’s time to call a pro.

3. Check for a Thermocouple Issue

Your thermocouple is the sensor that measures temperature. You can check for a few things on the thermocouple before calling a plumber to help you with a replacement. You can also skip calling a plumber if you don't want to deal with fiddling around with the thermocouple.

Rust

Rust is a common cause of thermocouple dysfunction. Here's how to troubleshoot a suspected rust issue on a thermocouple:

  • Turn off the gas valve to pilot

  • Remove cover plate 

  • Check to see if the thermocouple is buried in rust

Most people prefer to hire a local plumber at this point to service the thermocouple. However, you can attempt to brush or vacuum the burner element and pilot area if you know what you're doing. Just make sure you're letting everything cool completely before touching parts.

Using a shop vacuum over a household vacuum is preferred. You'll need to dump out the debris in a fire-safe way that includes leaving the vacuum and filter to ventilate for at least 12 hours.

You also have to be careful about not breaking off the pilot or gas fittings when cleaning the rust.

Pilot Flame

If rust isn't the issue, check that the sensor is properly immersed with the pilot flame. The thermocouple may have slipped out of place. If the thermocouple isn't sensing enough heat, it prevents the gas control valve of the main burner from opening.

Replacing the Thermocouple

Replacing your thermocouple is the last option if none of those troubleshooting points work. Thermocouples only cost between $10 and $20. Most plumbers will charge between $75 and $150 for labor on this type of job.

Should I Call a Plumber if the Burner on My Water Heater Won’t Work?

Many people don't want to deal with troubleshooting a burner because it can be a dangerous job. Not only could you damage your water heater if you do something wrong, but true to its name, it can be hot to the touch.

While it never hurts to check for the obvious fixes, you should avoid touching components of the heater if you don't have expertise in that area. Most local gas plumbers can diagnose the issue within a few minutes to give you an answer about whether you're looking at a simple fix, a sign your water heater is about to fail, or anything else in between.

Why is my pilot light on but no heat?

If there's a pilot light, make sure that it's lit and touches the thermocouple. If it's lit but the burners don't heat, feel the side of the furnace. If it's cool, the problem might be the thermostat, gas valve or control board. Make sure that the gas valve is on and that there's enough fuel.

Why is my water heater not giving me hot water?

What does it mean if the water heater is not producing hot water? It is possible that the circuit breaker tripped or a fuse blew, so check those first if you are not getting hot water from your water heater. If that's not the issue, then it could be that the heating element has burned out and needs to be replaced.

How do I know if my thermocouple is broken?

Failed Thermocouple Symptoms.
The first is signs of contamination on the tube, which can include discoloration, cracks, or pinholes..
Next, check the wiring for any signs of wear or corrosion like missing insulation or bare wire..

How long after pilot light is started will hot water come out?

How Long Does it Take to Get Hot Water. Once you've got your water heater back up and running, it's going to take awhile before you have hot water. How long depends on how large of a tank you have. In general, you should expect to wait between 30 to 40 minutes before your tank is fully heated.