How to Troubleshoot Your Gas Water Heater

How to Troubleshoot Your Gas Water Heater
May 17, 2012 Lorelie
Gas Water Heater

Gas Water Heater - Troubleshooting

Before doing any gas water heater DIY repairs and troubleshooting, one thing is certainly important – leaking natural gas and propane can be really dangerous.  When natural gas leaks, it tends to rise up.  As for propane, because it is heavier than the surrounding air, it tends to collect at the floor level.

If on case you think you smell a leaking gas close to the gas water heater, quickly turn off the pilot light, then close the main gas valve and DO NOT activate any electrical power switch, not even the light.  Call a plumber or a gas utility company immediately, from another room.  This is considered to be a very big problem wherein any presence of spark is dangerous.

Gas Water Heaters – Its Main Parts and How They Work

In order for you to properly identify common problems and symptoms associated with gas water heaters and how to troubleshoot and do repairs on them, it is essential that you become familiar with the main parts of a gas water heater and how it works.

  • The cold water from the house plumbing enters the heater tank, then through the dip tube, and fills the tank from the bottom up.
  • The control valve is responsible for keeping the small pilot light on.  When the temperature on the thermostat drops below the set temperature, it ignites the burner.
  • The hot flue gases run through the flue pipe that is situated in the middle of the tank and transfers the heat to the surrounding water, which makes it warmer and then finally hot.
  • The hot flue gases then get colder due to the transfer of heat and vent out either naturally or forced by the power vent.  The draft hood which is situated on the top of the hot water tank provides sufficient air for stable and proper gas combustion.
  • When you open the hot water tap for the purpose of washing the dishes or taking a shower, the hot water is drawn from the top of the unit, through plumbing to the open hot water faucet.
  • The TPR or the temperature pressure relief valve prevents extreme pressure from occurring in the tank, thus helping the excessive air or water to get out.
  • For tank flushing and draining, there is a drain valve present at the tank bottom.
  • Inside of the water heater tank, the sacrificial anode is used in order to prevent corrosion due to the water heating process.

With all the points mentioned above, it is now much easier to perform gas hot water heater troubleshooting.  In this regard, please take note that the troubleshooting methods that will be presented here are assuming only that the gas water heater was properly installed and was functioning correctly before any problems occurred.

Also, do take note that the hot water heater problems and troubleshooting tips stated below are related exclusively to the tank-type water heaters.  Keep in mind that in order to perform proper troubleshooting in gas water heaters, you need to have basic gas and electrical knowhow.

Gas Water Heater Troubleshooting Tips

Gas water heater problem #1:  No hot water

Solution and How to Repair:

Do check if you still have gas in your home or to the water heater unit.  The main gas valve may be closed.  If you suddenly experience no hot water, then your water usage may have exceeded the tank capacity.  If that is the case, then wait for the water heater to recover.

Another possible cause to this no hot water problem is that the pilot light has gone out.  Re-light the pilot flame according to the instructions stated on the unit.  If it won’t light up, then you need a new thermocouple.

Gas water heater problem #2:  Sooting

Solution and How to Repair:

When the gas water heater is running and you notice that both the chamber and flue have soot in them, even if the burner is still clean, do check out if there is a lack of air.  If in case all of these elements have soot in them, check for the following if present: excessive gas pressure, a wrong orifice might be used, there is loose gas burner or there is a loose gas connection in the burner assembly.

If in case the pilot flame or main burner flames are too small or too large, you may have dirt in the orifice or in the gas supply tubing, or the unit might have the incorrect orifice size.  Do follow the user’s manual for the right specs.

Gas water heater problem #3:  Condensation

When gas is burning, the flue gas cools to its “dew point”, resulting in condensation which can go back to the gas chamber.

What causes the flue gases to cool are: cold air supply and cool flue pipe surface.  This usually happens whenever a new water heater unit is filled with cold water for the first time around.

Also, condensation occurs if there is a large amount of hot water used in a short period of time and when the incoming water is very cold.

Another possible reason for condensation is the increased combustion efficiency, typically when above 87.5% of the flue heat is transferred to the surrounding water.

The signs/symptoms when condensation occurs are: water is still present around the heater even after its operation; there is water dripping, there are small black and red spots on the gas burner as well as on top of the heater and vent piping (which is the very reason why PVC or more expensive stainless steel vent pipes are used); when condensation occurs, you can hear a sizzling or frying noise on the burner.

  • Solution and How to Repair:
  • Raise the supply air temperature, the stored water temperature, or even its tank size (which makes sense if in case the existing unit is too old and poorly performing).

Gas water heater problem #4:  Lack of oxygen

For proper operation of gas water heaters, fresh air has to be delivered for gas combustion.  The air must enter the gas chamber from the base of the unit and then enter the flue vent from below the draft hood.

In case there is insufficient air flowing, potential problems may arise such as: yellow burner flame, sooting burner flame, pilot light outage, possible presence of carbon monoxide, and presence of a burnt gas smell in the room.

  • Solution and How to Repair:
  • The solution for this is in prevention – Check and make sure to provide enough air flow.  Check the flue vent and the base of the water heater unit for possible obstructions, and never cover it with an insulation blanket.

Gas water heater problem #5:  The burner won’t stay lit

Possible causes:

  • Dirty of clogged air intake
  • High ambient room temperature
  • The flame arrestor openings are blocked

Gas water heater problem #6:  The pilot light won’t light up or stay lit

Solution and How to Repair:

Check out if there is gas present or if the gas pressure is low.  In case there is a problem with the gas supply, call the utility company.

If there is air present in the gas line, bleed the air from the gas line (this should be done by a certified professional).

When trying to light up the pilot, ensure that the pilot light lever is open.

In case the pilot tube or orifice is clogged up, clean it.  If the thermocouple connection is loose with the gas valve or in the pilot light assembly bracket, simply tighten it with a wrench.  It may only need a simple adjustment.

The thermocouple needs to be properly secured and must be in contact with the pilot flame.  In case it is broken, replace it.  If you have a melted insulation on an igniter wire or there is a shorting of the igniter wire, replace it as well.

Take note that if the pilot light goes out sporadically, the following might be the cause of the problem: insufficient combustion air supply, condensation might be extinguishing the pilot light, inconsistent gas supply and pressure, or clogged or incorrect venting system.

Gas Water Heater Troubleshooting – Checking the Vent System

The venting system is extremely vital for the safety and efficiency of water heater operation.  The 90-degree elbow that is installed on the top of the tank draft hood can potentially minimize the vent efficiency by up to 50%.  It is advised that you install the vent system that rises straight up.  For horizontal vent pipes, there are some different installation rules that need to be followed (in that case, use the manufacturer’s manual for more information).

Another reason why the pilot flame will fail is because of decompression.  If air cannot enter as quickly as it is being used, the air pressure drops just below the outside pressure.  Therefore, it creates an effect known as “capping”.

The solution for this decompression issue is to simply create 2 air vents on the outside wall, one close to the ceiling and the other close to the ground level.  If you cannot do this, and the room is on the balcony for instance, provide appropriate venting opening on the door.

Take note that when you perform gas water heater troubleshooting and repairs on your own, ensure that the gas supply is turned off and always refer to the user manual.

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