Effect of installing larger water supply pipes to the water heater Guide to Hot Water Heater Noise Diagnosis
Find & fix noisy water heater problems
Water Heater banging, popping, rumbling sound diagnosis & cure

  • NOISE, WATER HEATER - CONTENTS: Water heater noise troubleshooting & repair. How to diagnose and cure water heater rumbling, clanking, cracking, or other hot water heater noises. Advice and photo-guide to de-liming and de-scaling hot water heaters - Scale formation in water heaters and methods of prevention. How to remove silt or debris from the hot water heater tank. Rate of deposition of lime and scale in plumbing systems
  • POST a QUESTION or READ FAQs about water heater noise troubleshooting and water heater scale and lime removal
  • REFERENCES
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Catalog of causes & cures of noises heard at or in water heaters, calorifiers, cylinders:

This article explains how to diagnose and cure noisy water heaters such as popping, hissing, crackling or banging. We describe the different types of sounds heard at a water heater, what they mean, their cause, and their elimination.

The sketch at page top is courtesy of Carson Dunlop Associates, a Toronto home inspection & home inspection education company. Used with permission.



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Noise Diagnosis & Repair Guide for Residential Hot Water Heaters

Measuring thickness of scale in water heater tank bottom (C) Daniel Friedman

[Click to enlarge any image]

List of Common Water Heater Noises & Their Usual Causes

If your water supply is hard (see DETECT HARD WATER), the minerals in the water tend to precipitate out at the hottest place in the plumbing system. Often this means that the water heater itself will accumulate solid precipitate of minerals.

Our photograph (left) shows our measurement of the thickness of mineral scale removed from the bottom of a six-year-old gas-fired water heater - more than 1/2 cm in thickness! The "lime" scale that forms in water heater tanks is composed principally of calcium and magnesium carbonate.

Relationship of Hard Water to Water Heater Noises

The hard water mineral deposits tend to collect as a hard skin on the bottom of the heater, interfering with heat transfer, increasing operating cost, and over longer periods, possibly weakening the bottom of the water heater itself.

Mineral deposits also accumulate on the electrodes of an electric water heater, eventually leading to the failure of the heating electrode. If you never remove the scale from a water heater tank the clanking or cracking noise heard at the water heater during operation may eventually cease when the scale solidifies, no longer trapping hot water and interfering with its movement upwards in the water tank.

However the development of a thick lime or scale layer in the bottom of a water heater also reduces the water heater tank life.

Other Water Heater Problems Caused by Hard Water & Scale Deposits

Why Should You Remove the Scale Deposits, Silicates, and Silt from Your Water Heater Tank?

Water heater scale after removal (C) Daniel Friedman

Our photo (left) shows chunks of water heater scale on the ground after removal from the water heater.

A.O. Smith gives six reasons (here we expand and add to them) for water heater tank scale removal, and the company points out that the reasons for scale removal and indeed the procedure for scale removal is (almost) the same regardless of the energy source: electric, gas, oil, solar water heaters.

Our "exception" is that solar water heaters and electric water heaters may have specific internal components (such as electric water heater electrodes) that will also need to be de-scaled or even replaced. [1]

Noisy water heater operation: Water heater noises, as we described above, may be the first thing people notice when the water tank scale layer has become thick enough to interfere with good water heater operation. But A.O. Smith and other water heater manufacturers cite additional reasons why removing water heater scale is important. Clean the water heater tank to reduce water heater noise.

Longer water heater "on" time & slower water heat-up rate: you can reduce the cost of making hot water with your oil, gas, or electric-fired water heater by removing scale from the tank bottom. The scale layer on the tank bottom (or on an electric water heater's electrodes) interferes with heat transfer into the hot water.

This means that the water heater will have to operate longer (and you will spend more on hot water costs) than necessary to re-heat incoming water. Clean your water heater tank to reduce your water heating cost by improving heat transfer into the water and correspondingly shortening the water heater "on" cycle time.

High water heater costs to operate, repair, replace:  for the same reasons as above: running the water heater longer just to get the water hot enough means higher water heater operating expense. In addition to higher energy costs to heat the water, unnecessary heater replacement, and in the case of electric water heaters, early failure of the heating elements are common results of heavy scale problems.

Hot water quantity has diminished - not enough hot water: by slowing heat transfer into the hot water in the water tank, the apparent hot water quantity will also be reduced, because incoming cold water is not heated as rapidly when occupants are drawing hot water out of the tank. Thus the incoming cold more quickly dilutes and cools the hot water that remains in the tank during use. Clean the water heater tank to increase hot water quantity.

Extend the water heater life: because scale on the water heater tank bottom insulates the tank bottom from the water inside the tank, the bottom of an oil or gas fired water heater will become hotter as the scale layer gets thicker. These increased temperatures weaken the water heater tank bottom and shorten the life of the water heater. Similarly, scale deposits on the electrodes in an electric hot water heater shorten the life of the electrodes. Clean the hot water tank regularly to extend its life.

Protect water heater warranty: if a water heater tank fails the manufacturer may not honor the water heater's warranty if the failure is due to the accumulation of excessive scale inside of the water heater tank. Water heater warranties typically indicate that the tank is warranted against leaks due to rust, corrosion, or chemical action of the water but the warranty will exclude a tank failure due to scale.

User dissatisfaction with the water heater because of less hot water, slower hot water recovery, and higher hot water costs lead to unhappy building occupants who may have no idea that a water heater scale problem is the cause. If dissatisfaction leads a consumer to replace a water heater that could have just been de-scaled, there may also be unnecessary heater replacement expense.

How Often to Remove Scale Deposits from a Water Heater

When the lime thickness reaches the hot water tank drain, there will be about one inch of mineral deposit on the tank bottom. If the water tank has a cleanout opening, when the lime thickness reaches that opening the mineral deposit thickness will be about 2". When you have observed the length of time required for lime to accumulate in your water heater you can set the appropriate maintenance schedule.

How the water heater scale is removed

See  WATER HEATER SCALE DE-LIMING PROCEDURE for a detailed water heater de-liming procedure. A summary of the de-scaling procedure is just below.

Step 1: Flush the Hot Water Tank to Remove Silt & Debris

The first step in curing water heater noises or poor hot water quantity is to turn off and flush out the water heater.

See Water Heater Flush Procedure for the full article on the detailed procedure for flushing out water heaters to remove scale, dirt, or debris - a step that can increase hot water quantity, temperature, and water heater life.

Watch out: don't tackle this water heater cleanout project on a Sunday night when you can't call a plumber or buy a replacement part. Water heaters, their heating source (oil or gas burner or electricity or solar hot water), and particularly their relief valves include critical safety components. Do not modify or remove relief valves, chimney connections, draft hoods, etc. as you may create dangerous conditions. Turn off all electrical and or gas power to the water heater and let it cool.

This means turning off electricity that controls the water heater oil burner or electric heating elements, or for gas fired water heaters, turning off the gas supply to the device.

Additional tips on draining a water heater tank can be found
at ELECTRIC WATER HEATERS

Step 2: Remove Scale Deposits from a Water Heater Tank - Scraping the Bottom of the Hot Water Tank

Water heater being flushed (C) Daniel Friedman

The second step in curing water heater noise or insufficient hot water is to remove scale or lime from the water heater tank. If the unit is an electric water heater, you'll also need to remove scale from the electric water heater elements.

See WATER HEATER SCALE DE-LIMING PROCEDURE for the full article on the detailed procedure for removing lime and water heater scale.

Safety Warning: never turn on a water heater's heat source before the hot water tank has been re-filled. Otherwise you may damage the heater or create a dangerous condition.

Be sure the water heater pressure and temperature relief valve is properly installed and is the proper type.

See RELIEF VALVES - TP VALVES.

Step 3: Prevent Scale Deposits in Water Heater Tanks or on Electric Water Heater Electrodes - Scale formation in water heaters and methods of prevention

The third step in stopping water heater noises, extending water heater life and increasing the amount of hot water that the heater produces, is to prevent un-wanted scale or lime deposits in the water heater tank or on an electric water heater's electrodes. Please see Water Heater Scale Prevention for the detailed article on this procedure.

The rate of deposition of scale inside of a water heater tank depends on

At Water Heater Scale Prevention we discuss in detail and provide research on the factors determining the rate at which scale and lime form in water heaters or on water heater electrodes.

How Mineral Deposits and Heating May Weaken a Water Heater Tank Bottom, Contributing to BLEVE Explosion

BLEVEs or boiling liquid expanding vapor explosions are discussed
at
 BLEVE EXPLOSIONS. Excerpts are below

Water heater tank explosions are rare thanks to the widespread requirement for and use of pressure and temperature relief safety valves. The photo (left) shows a hole in the roof made when a water heater exploded, becoming a rocket that passed up through the building.

But if the safety valve has been damaged, modified, or even omitted (as we saw on our neighbor's water heater), that condition, combined with overheating can cause a water tank to explode, creating a BLEVE - boiling liquid vapor explosion that releases tremendous force and causing extreme damage to a building.

Because repeated heating of the water tank bottom may combine with other conditions (such as corrosion or excessive heating due to mineral deposits on the tank bottom) to produce a weak water heater tank bottom, that is the part more likely to fail in an overheat and overpressure condition.

A failure at the water tank bottom may explain why a BLEVE can produce a water tank explosion that behaves like a rocket, sending the water tank skyrocketing up through a building.

Cures for Hard Water that Clogs Hot Water Tanks, Tankless Coils, and Plumbing Pipes

  1. WATER HEATER SCALE DE-LIMING PROCEDURE exactly how to get rid of water heater scale, a common cause of water heater noises.
  2. WATER HEATER SCALE PREVENTION - how to avoid scale formation in water heaters
  3. More water heater noises and some recommendations are in the Residential Gas and Electric Water Heater Handbook [PDF] provided by A.O. Smith and linked-to
    at REFERENCES

The articles at this website will answer most questions about diagnosing and curing noisy domestic water heaters and about the procedure to remove mineral deposits, lime, water scale, silicates, sulfates, aluminates, or silt and sand from a water heater tank. This website contains in-depth articles on inspecting, testing, and repairing problems residential hot water heaters of all types, including their parts, controls, and alternative sources for hot water as well as tips for improving hot water temperature, hot water pressure, and hot water quantity.

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Continue reading at WATER HEATER SCALE DE-LIMING PROCEDURE for electric water heaters or water cylinders, or select a topic from the More Reading links or topic ARTICLE INDEX shown below.

Or see WATER HEATER NOISE FAQs - questions & answers help diagnose more water heater noises

Or see HEATING SYSTEM NOISE DIAGNOSIS for a more broad list of noises traced to heating equipment


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WATER HEATER NOISE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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