How to Repair a Gas Water Heater

  • 01 of 07

    Repairing Your Gas Water Heater

    Gas Water Heater
    Gas Water Heater. © 2006

    Unlike tankless water heaters, standard tank-type water heaters use an insulated storage tank. 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 troubleshooting, make sure to prepare safely for the job by:

    • Turn off power to an electric water heater. Do this by turning off the circuit...MORE 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

    The Problem: No Hot Water Is Produced

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    Possible Causes:

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

    Possible Repairs:

    • Check gas pilot flame and pilot operation. Lighting a pilot flame on your gas water heater is similar to lighting a gas furnace pilot.
    • Re-tighten, reposition or replace the gas thermocouple.
    • Replace the gas pilot control valve.

    Continue to 3 of 7 below.
  • 03 of 07

    The 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 the 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, learn how to calc...MOREulate 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 the 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 a 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

    The 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

    The Problem: Rotten Egg Smell

    High Angle View Of Broken Egg Shells In Crate
    Silvia Elena Castañeda Puchetta / EyeEm / Getty Images

    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

    The 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

    The 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.