How to Repair a Gas Water Heater

  • 01 of 07

    How to Repair a Gas Water Heater

    Gas Water Heater
    Gas Water Heater. © 2006

    Unlike tank-less water heaters, standard tank-type water heaters use an insulated storage tank. The construction or anatomy of this appliance is explained in the tutorial Anatomy of the Gas Water Heater.

    Water heaters are generally very reliable but occasionally they do have problems.

    These problems can include:

    • No hot water
    • Inadequate hot water
    • Rust colored water
    • Rotten egg odor
    • Low rumbling or popping noise
    • Higher pitched whining
    • Water leaking around base of heater

    Before any troubleshooting is done,...MORE make sure to prepare safely for the job by doing the following:

    • Turn off power to an electric water heater. Do this by turning off the circuit breaker or fuse powering the heater.
    • Turn the gas pilot control valve to "pilot" setting.
    • Shut off the water supply to the water heater.

    Let's take a look at each problem and what possible causes and repairs exist.

    Continue to 2 of 7 below.
  • 02 of 07

    PROBLEM: No Hot Water is Produced

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    No Hot Water is Produced:

    Possible Causes

    • Faulty gas pilot
    • Faulty gas thermocouple
    • Faulty gas pilot control valve


    Possible Repairs

    • Check gas pilot flame and pilot operation. See How to Light a Gas Furnace Pilot for similar operation.
    • Re-tighten, reposition or replace the gas thermocouple.
    • Replace the gas pilot control valve.

    Continue to 3 of 7 below.
  • 03 of 07

    PROBLEM: Inadequate Hot Water

    Male Finger Turning Up Tankless Water Heater Temperature
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    Possible Causes

    • Unit is undersized for water heating demands
    • Broken or damaged dip tube allowing cold and hot water to mix in tank
    • Faulty plumbing installation has crossed cold and hot water connections
    • Gas supply or control problems

    Possible Repairs

    • Make sure water heater is not being overtaxed by hot water supply demands. The water heater should have 75% of its capacity as hot water (e.g., a 40 gallon WH should be used for a demand of 30 gallons). To determine required capacity see Calculating...MORE Fixture Flow Rates.
    • Undo cold water inlet and pipe nipple and remove dip tube. Check condition and replace if required.
    • Check for crossed connection by turning off water supply to water heater. Open a hot water faucet. If there is water flow, then there is a crossed connection somewhere. Check for a hot water line connected to a cold water connection on the water heater or appliances such as washer, dishwasher, faucet or shower valves.
    • Check for proper flame from the burner. A natural gas flame should be a bright blue with the tip of the flame having just a tinge of yellow. A propane flame should have a bluish green flame with a tinge of yellow at the tip.

    Continue to 4 of 7 below.
  • 04 of 07

    PROBLEM: Rust Colored Water

    Sacrificial Anode Rod for Water Heater
    Sacrificial Anode Rod for Water Heater.

    Possible Causes

    • Corrosion occurring inside glass lined tank
    • Sacrificial anode rod is failing (anode rods dissolve slowly to prevent rusting in the tank)

    Possible Repairs

    • Replace sacrificial anode rod with magnesium anode rod. Anode rods are available from a plumbing supply house.

    Continue to 5 of 7 below.
  • 05 of 07

    PROBLEM: Rotten Egg Smell

    High Angle View Of Broken Egg Shells In Crate
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    Possible Causes

    • Bacteria in the tank sediment fed from hydrogen gas created from decay of sacrificial anode.

    Possible Repairs

    • Flush water heater
    • Using a hydrogen peroxide solution of 2 pints 3% peroxide to 40 gallons of water, treat tank and run some of the solution into water lines.
    • Let peroxide solution set in tank and pipes for 2 hours. Solution is not toxic and requires no rinsing.
    • If problem persists, replace anode with a zinc-alloy anode.
    • If problem still remains, replace water heater with a...MORE plastic lined tank type.

    Continue to 6 of 7 below.
  • 06 of 07

    PROBLEM: Low Rumbling or Popping Noise

    Son watching father check hot water tank with energy application on digital tablet
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    Possible Causes

    • Noise heard is the sound of boiling water. Excessive buildup of sediment in the bottom of the tank is causing overheating of tank bottom and boiling of water to occur.

    Possible Repairs

    Continue to 7 of 7 below.
  • 07 of 07

    PROBLEM: Water Leak Around Base of Heater

    Close-up of drain pipe leaking water
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    Possible Causes


    Possible Repairs

    • Place bucket under overflow pipe. Open and flush T&P valve clear of debris. If leak remains from the valve, replace the valve.
    • Reduce thermostat setting to prevent tank overheating and opening T&P relief valve.
    • Inspect the bottom of the tank by looking through the...MORE combustion chamber. If water marks or heavy rusting is noticed or if water is noticed setting in combustion chamber bottom, then the water heater needs to be replaced.