Pilot Light ON But No Hot Water – Troubleshooting Guide

If you have a gas water heater, you might be used to thinking that if the pilot light is on, then everything is ok with the whole system. But that is not always the case, as you might not have any hot water, even when the pilot is working perfectly fine. 

The pilot light might be failing to ‘communicate’ with the burner due to a malfunctioning gas valve and a corroded burner line and jet. Your water heater also won’t be able to produce hot water in case the thermocouple is faulty or there is sediment build-up in the tank.

Why Will My Hot Water Not Turn On?

If you have a gas water heater, then you can try doing this:

  • Check the thermostat
  • Consult the weather forecast (sudden cold can affect the performance of your unit)
  • Relight the pilot light, if it had gone out
  • Inspect the gas line (the gas valve should be open and the line shouldn’t have any kinks)
  • Fix the thermocouple (if the flame fails to stay on, you might want to adjust or replace the thermocouple)
  • Check the pilot flame’s color (if it’s yellow, then there’s a gas-to-air ratio problem and you should call a technician)

Read: Why Gas Hot Water Heater Is Not Heating? – Troubleshooting Guide

Why Is My Gas Working but Not Hot Water?

Check if the pilot light is staying lit.

If the flame keeps going out, then you might need to clean or unclog the orifice

If that didn’t help, try resetting the high-limit switch

Finally, a defective thermocouple might be to blame. You might have to replace the element; thankfully, it’s relatively inexpensive. 

Read: Gas Water Heater Thermocouple Possible Issues

Why Am I Getting Heating but No Hot Water?

Check the controls

If there has been a power outage, you may have to reset the water heater. Also, do check the device’s thermostat control.

Check the diverter valve

The diverter valve is the component that makes the hot water supply ‘switch’ between the radiators and the taps. The valve can get damaged or stuck, and this, in its turn, can cut off the hot water supply.

Try running the tap at a slower rate

When it’s cold outside, water heaters (especially, combi boilers) can have a reduced water flow between the heat exchanger. You will still be receiving hot water but at a slower rate.

Read: Why Water Heater Is Leaking?

Why Is the Hot Water Not Working in My Shower?

If you have an issue with hot water only in the shower, then it looks like either your anti-scald device is set too high or the shower mixing valve had gone bad.

A lot of faucets have anti-scald devices – safety features that limit how far the shower handle can be rotated in the hot water direction.

In such a case, you would have to locate the device and turn it to the right until the water temperature gets back to normal.

Hint: not all faucets have an anti-scald feature. If you can’t seem to find this plastic element, then the chances are high that you don’t have one.

Another thing that might have gone bad, is your shower mixing valve. This device is able to control the temperature of the shower by blending hot and cold water.

If you don’t feel comfortable disassembling the shower fixture, then you might want to call a professional.

Read: Is Furnace And Water Heater The Same?

How Do I Fix No Hot Water?

  1. The first thing that you should do is check the gas supply.
  2. If you do have gas flow, but the pilot light is not lit, then check if the thermocouple is tightly connected to the gas line and if its tip can reach the flame of the pilot.
  3. You might have to clean the pilot’s orifice.
  4. The gas valve is another component that can prevent the gas from reaching the pilot. If it’s malfunctioning, you would have to replace it.
  5. If the burner is dirty, you would have to clean it.
  6. Finally, check the flue and remove any obstructions and/or dirt.

Keep on reading to find out what to do if the pilot light on but no hot water.

How Long Does It Take for Hot Water to Come Back After Pilot Light?

If you have a tankless unit that heats up the water ‘on demand’, then you’d be able to get hot water in a matter of seconds. Of course, that will happen only in case your unit is working correctly.

The temperature of the incoming water, the settings, the location of the water heater, and the length and diameter of the piping are the things that are going to affect heat up time.

How Long Does It Take for Hot Water to Come Back Gas?

If you have a gas water heater with a tank, then it might take the water that has been just fed into the tank around 30-40 minutes to heat up. 

However, do bear in mind that the exact time would depend mainly on the capacity.

Pilot Light Stays Lit but Burner Won’t Light

Here are the main reasons for your burner not to ignite, when the pilot is lit:

  • A malfunctioning gas control valve – the element can fail to recognize that the pilot is on.
  • A dirty or corroded thermopile – this is the burner’s component that should be sensing the flame.
  • The burner’s line and jet are corroded
  • One of the burner’s switches is faulty – the majority of burners have a flue gas spill and a flame roll-out switch.

Pilot Light on But No Hot Water

This might happen if you forget to turn on the gas valve from the pilot. You need the gas line to the burner to be turned on for the water heater to function – turning the knob on the pilot will only show you that the pilot is functioning correctly.

If the thermocouple is malfunctioning, it won’t be able to run a voltage through it that ‘triggers’ the burner. You would have to either adjust or replace the thermocouple.

In case your tank has a thick layer of sediment build-up, the water heater might not be able to warm up the water at all, even if all the other elements are in great condition.

Hot Water Heater Burner on But No Hot Water

  • The pipe has frozen somewhere along the hot line
  • There is a blockage in the water line
  • One of the valves is closed
  • Incorrect thermostat settings
  • Sediment build-up

Gas Water Heater Thermocouple Issues

If you can see that the pilot light is on, but your water heater is not able to deliver any hot water, then there might be an issue with the thermocouple

This element is, basically, a probe with a copper tube that is screwed into the gas valve. 

A correctly operating thermocouple should measure anywhere between 30 and 40 millivolts at the connection end. In any other case, you would have to replace the component (you might want to leave that to a professional). 

Read: The Best Temperature For The Water Heater And Why?

How Do I Reset My Gas Hot Water Heater?

If your gas water heater doesn’t have a reset switch above the thermostat, then you would have to reset the pilot light.

Where Is a Diverter Valve Located?

Combi boilers have diverter valves that open and close the water flow to the radiators and taps and showers.

You’ll find a level right behind the bath taps and the actual mechanism behind the boiler’s lid (run the hot water tap – the component that’ll move is the diverter valve).

Will an Airlock Clear Itself?

Your central heating or hot water system has an airlock in case it has air trapped in it. This bubble of air can get caught in the pipework; as a result, you’ll have some problems with the water flow. 

Sometimes, airlocks do end up fixing themselves, but if you have found out that a bubble of air is the thing that is causing the problems with your water system, then it’s better to take care of the issue as soon as possible (airlocks can cause overflows and blockages).

Do Hot Water Heaters Have Pilot Lights?

Electric water heaters do not have pilot lights.

Moreover, not all gas units have a standing pilot nowadays. Some use electronic ignition that ignites the gas.

To find out, if your water heater has a pilot light or not, look beneath the water tank (you might need to remove the access panel).

How Do You Spark a Hot Water Heater?

  1. Turn off the gas by turning the pilot knob to the ‘off’ position. Give the system 5 minutes to get rid of any build-up gas.
  2. Turn the water heat dial to ‘low’ and the pilot dial to ‘pilot’.
  3. Turn the pilot dial downwards and simultaneously push the igniter button.

Let go of the latter, but keep pushing the pilot button for 30 seconds more.