Water Heater - Gas - Detailed OperationHow to trouble shoot your gas water heater and solutions of hot water heater problems |
All About Water Heaters and Water heating
Electric Water Heater Operation Electric Water Heater Repair Traditional Type Cold Water Return |
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Water Heater - Gas Models
Natural gas water heaters are the most common type of water heater due to the economy of burning gas to heat water. In earthquake prone areas one should tie the tank to the wall securely so if an earthquake strikes, the tank won't tip over breaking the gas line and possibly igniting a fire. All the Details About How It WorksMost of us tend to take our water heaters for granted. After all, it’s just a tank full of water with a gas burner inside. But once you add thermostats, PT valves, drain valves, dip tubes, and anti-corrosion anodes, you have a system that has plenty of potential problems. A water heater can do some weird thingsA typical 40 gallon gas water heater is a cylindrical tank, having a hemispherical fire box underneath, with the flue (chimney) going up through the center of the tank. The gas burner, pilot light, and thermocouple are at the bottom of the firebox. The pilot light is mounted on the burner, with a thermocouple located where it will be heated in the flame from the pilot light. Thermocouples keep the pilot light litA small electric current that tells the gas control valve that the pilot light is burning is produced by the thermocouple. The thermocouple stops producing the electric current if the pilot light goes out letting the thermocouple cool off. The gas valve feeding the burner will not open unless the thermocouple current is flowing. In order to produce enough current to hold the valve on, the thermocouple has to be very hot. That is the reason you need to push the button for so long when re-lighting the pilot light. The water temperature is controlled by the thermostatIn the lower portion of the tank there is a thermostat . The thermostat The thermostat tells the burner to come on when the lower temperature set point is reached, and turns it off when the water reaches full temperature. There is normally a control knob to set the temperature to a warm, medium, or hot temperature. The dip tube is an important part of your water heaterThe dip tube is a long skinny plastic tube that fits into the inlet and reaches down to the bottom of the tank. The cold water coming into the heater flows through the dip tube to the bottom of the tank. If the dip tube breaks, the cold water coming into the water heater can flow a few inches to the side and leave through outlet. This causes the water temperature to be low, and it can seem as though your water isn’t getting hot, just warm, or another symptom is that is seems you run out of hot water very quickly. Since the cold water flowing into the heater is going right to the bottom of the tank where the thermostat is, running even a gallon or so of hot water out of the hot water tap can cause enough of a drop in temperature to activate the thermostat, turning on the gas valve, and igniting the burner. Hot water stackingShort uses of hot water that occur frequently can cause the burner to cylce on and off, causing the water at the top of the heater to keep getting hotter with each cylce. This effect is called “stacking”. This stacking can cause the water to get so hot in the top of the tank that the Temperature Pressure Relief valve opens. The TP valve, also known as a TPR valve or other names is a safety device.The TP valve opens to relieve pressure if either the pressure gets too high or the temperature gets too high. This prevents the water heater from exploding if something goes awry. The TP valve is located on the side of the tank near the top. Typically the outlet of the TPR valve is plumbed down to the floor to prevent scalding accidents if one is standing near the heater when the valve discharges. As the water heats up, it expands, and as it expands some of the water gets shoved back into the source, such as the water main. If there is a check valve or some other obstruction between the heater and the source of cold water, provisions must be made to prevent a pressure build up. That usually calls for an expansion tank. Water heater expansion tanksAn expansion tank is a pressurized tank usually with a rubber bladder inside or a diaphragm in the middle. As the water expands it moves from the heater's tank into the expansion tank and thus doesn’t build up to dangerous pressures. Local building codes often call for the output of the T&P valve to be piped down to near the floor, or outside to the ground, to avoid anyone getting scalded if they happen to be near the water heater when the TP valve opens. What is sediment and where does it come from?When your water heater heats the water, dissolved minerals in the water can precipitate out settling to the bottom and forming sediment. You sometimes hear people say that you shouldn’t drink water that has passed through the water heater. If you live in an area with hard water, over time your sediment can build up to pretty significant levels. You often hear that a build-up of sediment reduces the efficiency of your heater, but it doesn’t have much impact. If the sediment interfered with the transfer of heat from the firebox to the water, and as a result more heat leaked out of the firebox or went up the chimney, then the efficiency would be reduced. Instead, the heat just passes through the sediment into the water and no reduction in efficiency occurs. However, if the buildup is large, the amount of water held by the water heater is reduced, so you could run out of water more quickly. Noises such as popping sizzling and gurglingPopping and other odd noises occur when steam bubbles form underneath the sediment layer It won't damage anything, but it can be annoying. Sizzling noises can be caused by condensation dripping onto hot metal parts. If you live in a hard water area, you might want to flush the water heater once a year or so. The anode protects against corrosionWater heater tanks are internally coated with epoxy or have a glass lining. This is to prevent rusting and corrosion. To further fight corrosion water heaters have a magnesium or aluminum rod called an anode inserted into them from the top. The idea is that the anode will corrode instead of the tank. Eventually the anode can wear out and need to be replaced. Bad smelling water - rotten egg smellAnaerobic bacteria can get into water heaters, and can react with the magnesium or aluminum in the anode, forming hydrogen sulfide gas. The gas is harmless, but has a rotten egg smell. This is more common with well water than from water mains. Some people say that replacing the magnesium rod, the more common one, with aluminum can help. There are also some special (and expensive) anodes that are supposed to solve the problem. Anther method that works is to sterilize the tank and the hot water pipes with bleach or hydrogen peroxide. However, the bacteria can come back, especially if you go away for a time and the water just sits in the heater for days or weeks. Other than the awful smell the bacteria will not harm humans. Drain valve - metal is betterAt the bottom of the tank there is a drain valve. If you live in an area with hard water and you have a sediment problem, then you should probably replace the cheap plastic drain valve that most water heaters come with now days with a full flow ball valve. This will make the tank much easier to drain and flush. |
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