My gas water heater is certainly leaking gas. I can smell it.

Using the image below, it seems like it might be coming from the red circle where the dial connects to the thermostat or the blue circle where the manifold tube connects to the thermostat. I don't smell anything around the green circle, the pilot tube.

Is it even possible to leak where the red circle is? If not then I assume it is the blue circle, the manifold tube. Is there a trick to tightening the manifold tube, like there is for water pipes? I have it as tight as I can get it right now. If it is leaking from the red circle area do I have to replace the whole thermostat?

Water heater thermostat

  • I don't know the answer to all your questions, but the dial can certainly leak - behind it is the actual valve that turns the gas on and off. Where does the gas come in from?
    – Ariel
    Feb 6, 2014 at 6:45

3 Answers 3


Time to call a professional; either a plumber or the local fire department. They can use more sophisticated leak detectors to pinpoint the leak, and know how to do so safely. Leaking gas is not something to trifle with.

Liquid leak detectors (the type that bubble up when gasses are leaking) are great for simple threaded connections, but you've got a whole host of potential leak sources, some of which appear to be not conducive to slathering soapy water on. I think an electronic combustible gas detector is in order.

  • I'm not going to pay hundreds of dollars for a "professional" to tell me what I already know. When I cut the gas to the water heater the smell goes away. The problem is with one of the easily replaceable parts on the water heater.
    – user19565
    Feb 6, 2014 at 18:54
  • 2
    "I have it as tight as I can get it right now" There are some connectors that are designed to be torqued only to a specific point. Over-tightening would cause these connectors to leak. I don't know if there are any gas-line connectors in this category; do you?
    – DJohnM
    Feb 6, 2014 at 19:18
  • 2
    @fredsbend the professional would presumably tell you what you don't know, i.e. where exactly the leak is, and what needs to be replaced.
    – mac
    Feb 6, 2014 at 19:37

You can use a mixture of water and dish soap to discover where it is leaking. I'm not sure of the ratio but you want it the consistency to be somewhat thicker than water, maybe 1 cup water and one Table spoon dish soap. Combine in a container and gently swish around until it is evenly distributed. Once you have the solution made apply liberally to the area you suspect. If it is leaking there you should see bubbles from the gas leak. If it is leaking at the red area. you would need to replace the valve.


Buy a leak reactant, because soap and water is not good enough: a micro bubble coccoon will appear at the leaks. Call the gas company