The gas heater works by a law of physics called convection which loosely paraphrased, states that heat rises. Heat rising and convection is a simple rule that you live with everyday and a hot container is no exception.
Cold water is supplied to the tank and injected at the bottom of the tank through a dip tube. The denser cold stays there and is heated by the gas burner.
As the liquid heats up, it naturally rises and is drawn off by the hot discharge pipe. You'll notice that the hot pipe is much shorter than the cold pipe.
This ensures that only the hottest liquid is being used from the container. The hot heater has simple parts and some safety features.
Cold water is provided to the tank by a cold supply line and controlled by a shutoff valve. It is important to know where the supply shut off valve is located so maintenance can be performed on the container.
This is the business end of the heater and the hot liquid line is what supplies all your sinks, tubs, showers and appliance needing hot water. The container jacket itself is made of steel and encloses a pressure tested storage tank.
Between the storage tank and the container jacket is insulation to reduce heat loss of the heated water. It is a good idea to supplement the insulation by adding a fiberglass insulation container jacket to the outside of the heater.
These are inexpensive and easy to install. Inside the tank you will see a dip tube, which is where the cold liquid supply enters the container to be heated by the gas burner.
Since cold air and cold water are denser than hot, the cold water sets at the bottom of the tank until it is warmed by the burner and heated enough to rise to the top of the container where the hot hangs out. In glass-lined containers there will also be a metal rod in the container called a sacrificial anode.
The anode rod is bolted and fastened to the top of the container and extends deep into the container. Its purpose is to draw corrosion to itself instead of the metal tank.
Some models do not have a separate anode but combine the function of the anode with the hot outlet. Plastic lines containers do not have an anode
The natural gas or propane is supplied by a pipe having its own gas shutoff valve. Just like you need to know where the supply shutoff valve is located, you need to know where the gas line shutoff is located too.
The gas line fees into a gas burner control module that serves as a kind of thermostat for the heater. It also controls the ignition of the pilot light.
From the control module we now proceed to the gas burner assembly. This includes the pilot light and gas burner itself.
The pilot light and burner adjustment are key to proper and energy efficient operation of the heater. The gas flame should about 1/2 inch in height and should have blue tips.
The exhaust flue exhausts combustion gasses from the burner and it serves as a type of heat exchanger helping to heat the liquid in the storage tank. The flue must be properly exhausted to the outside and there are specific code requirements for the type of flue construction and acceptable details.
A safety feature of the hot water heater includes the pressure relief valve and discharge pipe. The purpose of this valve is to relieve excessive temperature or pressure builds up inside the container if it approaches the limits of the container's safe design range.
This valve is located on top of the tank and often is threaded directly into the container top itself. To test the valve, lift up on the handle slightly and hot liquid should discharge out of the overflow pipe.