Gas hot water cylinder – no hot water

Causes

No gas

Gas pilot light has gone out

Faulty gas thermocouple

Faulty gas pilot control valve

Common

Listed under: gas, water heating, hot water cylinders, Services

Cause

No gas

Repair

  • check that the gas supply is not switched off at the meter and confirm with the energy company that gas is being supplied to the property
  • if the gas is from an LPG cylinder, check that there is gas in the cylinder and that the valve is open. You may need to bleed air out of the gas line if the cylinder has recently been replaced, or has not been used for a long time
  • if the water heater has a wall-mounted control panel, check that this is switched on. If there has been a power cut, you may need to turn the controller back on
  • gas regulators can also stick where appliances are used infrequently (such as gas heaters) and may need replacing by a registered gas fitter (the pressure needs to be reset to the appliance requirements)
  • check if the appliance supplier has a troubleshooting page on their website – several do
  • if you smell gas or you suspect there may be a gas leak, follow the advice on this page

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Cause

Gas pilot light has gone out

Repair

  • the pilot light ignites the gas burner in a water heater
  • with many gas water heaters it is possible for homeowners to relight a gas pilot that has gone out
  • the instructions for doing this may be on or inside the cover over the burner. If not, check the paperwork that came with the water heater for instructions. If you don’t have that, check whether the appliance supplier has a troubleshooting page on their website. If not, or you can’t understand the instructions, give the supplier a call for advice. In some cases they can explain over the phone what you need to do
  • modern gas water heaters typically have a spark or igniter button to light the flame. You hold down the pilot button and then light the pilot with the igniter. You may hear a clicking sound. You normally have to hold down the pilot button for at least 20–30 seconds for the pilot to light properly
  • do not try to light the water heater if you can smell gas in the room. Follow the advice on this page
  • be aware that there are strict limits on the work householders can do themselves. Installing or replacing gas appliances and fittings, or carrying out major repairs, can only be done by a registered gas fitter

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Cause

Faulty gas thermocouple

Repair

  • the gas thermocouple is a metal temperature sensor that lets gas flow through to the burner when it senses heat from the pilot. If it detects that the pilot has gone out, it turns off the gas as a safety measure. The thermocouple may not work properly if it is not positioned properly, is damaged or dirty
  • a thermocouple may need to be repaired or replaced depending on the problem. Call the company that supplied the water heater, or any registered gasfitter
  • be aware that there are strict limits on the work householders can do themselves. Installing or replacing gas appliances and fittings, or carrying out major repairs, can only be done by a registered gas fitter

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Cause

Faulty gas pilot control valve

Repair

  • call the company that supplied the water heater, or any registered gasfitter

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