Why Is My Hot Water System Not Working?


You’d be surprised at the number of people who don’t know where their hot water system is until the day it breaks down. If that’s you, don’t worry you are not alone.

There are a few things that you can do yourself to prevent or deal with minor issues that come up with your hot water system.

Common issues with hot water systems include:

  • Pilot light has gone out
  • Leaking cylinder
  • Dripping from relief valve
  • Faulty thermocouple sensor

Most hot water units have a life span of about five to fifteen years. Some more, some less. There are a few things that determine that. Sometimes it’s water quality or how much it’s been used. Some brands might last longer than others.

Energy Safe Victoria recommends a service of all gas appliances every two years. People do get their heaters checked but with hot water systems, it is a case of out of sight, out of mind. Most of our call outs for hot water systems are on that sad day when there is rudely no hot water for the morning shower.


Flammable Materials

Start with a quick but important check – make sure there are no flammable materials around your hot water system.


Pilot Light Has Gone Out

To light a pilot light you normally hold down the pilot button and light the pilot with the piezo igniter. You have to hold down this button for 30 seconds, before releasing. If you release the button and the pilot flame and it goes out, that means the thermocouple is faulty. A thermocouple can usually be replaced for under $200.

Another thing that happens is a freak gust of wind can just blow out the pilot light. It needs to be re-lit by following the lighting instructions, usually on the inside of the front cover of the heater unit.

Most people can light the pilot flame, but there is a bit of a procedure to it. If you follow the instructions it will work, and the instructions are nearly always inside the cover. There’s a cover down the bottom, which you remove to get to the burner. On the inside of that cover, you’ll find the instructions to light the pilot flame. A lot of people don’t read the instructions correctly and accidentally miss a step. In cases like that the pilot light won’t work.


Leaking Cylinder

A common problem we see in hot water systems is that the cylinder is leaking, and this can put out the pilot flame. You can tell if that’s a problem because you can hear hissing when you go up to the hot water unit. That sound is the water hissing out somewhere inside the cylinder. If we open up the cover and there’s water inside, that’s a sign that the unit needs replacing, it’s not repairable. This leaking cylinder problem happens to all hot water units eventually and that is the end of them.


Water Dripping or Pooling from Relief Valve

There’s a relief valve normally connected to the top side of the unit. That should only be dripping when the hot water unit is being heated. It shouldn’t be running all the time. If your relief valve is running all the time, it’s a problem. If you notice water around the bottom of the heater, coming out the front cover, that’s definitely not a good sign and you could be headed for trouble.


Faulty Thermocouple Sensor

Usually, when someone says their hot water unit is not working, it’s the thermocouple that’s playing up. The thermocouple senses when the pilot flame is on. It is a safety device – if the pilot flame gets blown out, the thermocouple sensor cools down and that in turn shuts off the gas.

It often happens that after a while the sensor can play up in hot water systems. The default action when they don’t work is that the gas is shut off. You’ll need a gas plumber to fix a faulty thermocouple.

If you have any other issues with your gas or electric hot water system that aren’t covered here, get in contact with us today! Our experienced plumbers in Coburg, Preston, Thornbury & other Melbourne locations are available to resolve all your hot water systems repairing needs.