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 Guide to Hot Water Heater Anodes & Dip Tubes - Inspection, Diagnosis, & Repair
- ANODES & DIP TUBES on WATER HEATERS - Water heater anode or water heater dip tube inspection & replacement
- A bad water heater anode can produce a sulphur odor in hot water
- A worn out water heater anode shortens water heater life
- A leaky water heater dip tube can cause less hot water delivery to the home or debris in the water supply piping
- What is the difference between a water heater dip tube and the sacrificial anode? Are they the same part?
- How to inspect, diagnose, & replace water heater anodes and dip tubes
- WATER HEATER DEBRIS FLUSH - separate article
- WATER HEATER FLUSH PROCEDURE - separate article
- Questions & Answers about water heater anodes & dip tubes: water heater odors, corrosion, leaks, & tepid hot water troubleshooting
- References
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
This article gives a definition of water heater anodes or dip tubes, explains what they are for, how they work, and what goes wrong with anodes and dip tubes. A corroded or damaged dip tube or water heater anode can cause loss of hot water, water heater odors, and even debris showing up in the building water supply. The articles at this website will answer most questions about residential and light commercial water heaters as well as many other building plumbing system inspection or defect topics.
Page top water heater drawing showing the sacrificial anode on a water heater is provided courtesy Carson Dunlop Associates, used with permission.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Check the Sacrificial Anode & Dip Tube of Your Water Heater Tank
 Reduced hot water pressure and flow and also sulphur smells or similar water odors in the hot water supply as well as debris in the water supply system might all be traced to problems with a water heater anode or dip tube. Accumulated debris in a water heater, and debris from a corroded or disintegrating hot water tank dip tube or hot water tank sacrificial anode can also block the hot water outlet opening, resulting in low hot water pressure in a building.
Below we discuss the water heater anode and water heater dip tube in detail. Also see WATER HEATER DEBRIS FLUSH This article describes the diagnosis and cure of debris in the building water supply traced to a deteriorated water heater dip tube/anode. Also see Water pipe clog diagnosis and WATER HEATER SCALE - De-Liming Procedure for further diagnosis and repair procedures of bad hot water pressure and flow in a building. But if both cold water pressure/flow and hot water pressure/flow are slow or inadequate, readers should see WATER PRESSURE LOSS DIAGNOSIS & REPAIR.
Functions of a Water Heater Tank Dip Tube:
The water heater tank dip tube, often made of a special metal to combine its function with that of a water heater tank sacrificial anode (to reduce water tank corrosion and leaks) performs these functions:
- Incoming cold water is placed at the bottom of the water heater tank, closest to the heating element or burner
- Incoming cold water does not dilute and cool down the outgoing hot water which by natural convection will normally rise and be found at the top of the hot water tank
- Corrosion protection: in some (not all) water heaters, construction of a hot water tank dip tube of an intermediate metal (perhaps zinc) will permit it to function as a sacrificial anode in the water tank to reduce the corrosive effects of hot water on the water tank body itself - this makes the water tank last longer. We discuss the hot water tank sacrificial anode and dip tube in more detail at Check the Sacrificial Anode & Dip Tube of Your Water Heater Tank.
Functions of the Water Heater Anode
By inserting into the water heater tank a rod made of a metal which is more readily corroded than the steel of a steel hot water tank, the sacrificial anode protects the hot water tank from early failure due to corrosion. An illustration of the water heater anode is shown at the top of this page.
Low Hot Water Temperature Traced to Depleted Combination Dip-Tube & Sacrificial Anode
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At Temperature of Hot Water is Too Low we explained that a leaky dip tube in a water tank can result in hot water temperatures that are too low.
But the dip tube on many water heaters also functions as a sacrificial anode, as we show here.
Here Carson Dunlop's sketch shows the location of the sacrificial dip tube on an electric water heater. Cold water is shown entering from a pipe behind the heater and entering at the bottom of the water tank.
But some water heaters use a "dip tube" that may also serve as the sacrificial anode.
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Sulphur or Rotten Egg Smells in Hot Water Supply Traced to Water Heater Anode Problems
The role of the sacrificial anode is to protect a glass-lined steel water heater tank itself from corrosion - the water heater anode rod will gradually deteriorate or basically "dissolve" over the life of the water heater. The rate of water heater anode depletion depends on the chemistry of the water supply (more aggressive water is more corrosive), and the amount of usage of the water heater - how much hot water is used in the building.
Watch out: if the water heater sacrificial anode rod completely dissolves or depletes, the water tank itself is no longer protected from corrosion and the tank may be damaged and its life significantly reduced.
If your hot water smells like rotten eggs, and especially if it's only the hot water, not also the cold water supply, you should definitely check the condition of the sacrificial anode on the hot water heater, no matter what kind of water tank you've got installed.
If the building water supply contains dissolved hydrogen sulfide gas (H2S), (also potentially explosive - see Hydrogen Sulfide Gas), then the combination of water chemistry and the presence of the sacrificial anode in the water heater tank can produce black debris in the water supply and an increased level of sulphur or rotten egg smells in the building hot water supply. In fact if there is significant H2S in the water supply even the cold water may smell like rotten eggs. In our experience with private well water that contained H2S, the odor level varied by time of year, level of the water table in the ground, and usage of the well. Often returning from a month of vacation the homeowner would notice a stronger rotten egg smell in the building water supply.
If your water supply contains high levels of hydrogen sulfide, enough to smell, you should check with your plumber or your water heater manufacturer about purchasing and installing a special sacrificial anode that can reduce this smell problem in the building hot water system. Additional water treatment to remove sulphur may also be needed.
Corrosive Water Supply Reduces Anode & Water Heater Tank Life
If your water supply happens to be highly conductive or corrosive (see WATER TESTING GUIDE) then the dip tub/sacrificial anode in the water tank may indeed corrode away until it leaks (dropping the hot water temperature) or disappears entirely.
Another cause of H2S odors in hot water may be traced to homes that use a water softener to treat their incoming water supply. Water that is high in salt ions (a water softener may replace calcium or magnesium with sodium or salt ions in the process of "softening" a hard water supply), can be extra corrosive in the water heater and can reduce the life of both the sacrificial anode and the water heater tank itself.
At Odors in Water we discuss the general problem of diagnosing and curing odors in water; also see Odors, Smells, Gases in buildings-Diagnosis & Cure.
We provide a detailed list of sewer and sulphur gas odor sources at Sources of Sulphur Odors in buildings. Also CHINESE DRYWALL HAZARDS discusses Chinese drywall odors, sulphur smells, and corrosive outgassing hazards in buildings. Major costs to remove this product, repair or replace electrical wiring, plumbing, and HVAC components may be involved, and there may be immediate safety hazards due to damaged smoke detectors or carbon monoxide detectors in buildings where Chinese drywall outgassing has caused damage.
Procedure to inspect a water heater Sacrificial Anode or Dip Tube
 In our photo (left) our pencil is pointing to the water heater sacrificial anode fitting, viewed looking down on the top of the water heater. Often the word "anode" will be found embossed into the steel water heater top at this location.
In this case the sacrificial anode is a separate component that can be removed and replaced on the water heater tank.
The dip tube, not directly visible, is below that blue plastic ring that marks where cold water is entering the water heater tank.
Regardless of whether your water heater is electric, gas fired, oil-fired, or indirect fired from another heat source the sacrificial anode inspection and change out procedure is similar. We outline the procedure below, but for details also see DRAIN a WATER HEATER TANK
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- Turn off the water heater
- Close the cold water valve that lets water enter the water heater tank
- Open a nearby hot water faucet to relieve water pressure in the water tank.
- Remove the sacrificial anode - which may mean removing the combined dip-tube/sacrificial anode at the top of the water heater tank. On many water heaters the dip tube, used to direct incoming cold water to the bottom of the water heater tank, is also the sacrificial anode. So disconnecting some plumbing fittings at the cold water inlet may be needed.
- Install a new sacrificial anode in your hot water heater tank - be sure that your plumbing connections are properly cleaned and doped (or use teflon tape) - so that you won't have to do this procedure all over again.
How Often Should the Water Heater Sacrificial Anode be Inspected?
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 Water heater installation guides we surveyed gave water heater anode rod inspection (and replacement if needed) intervals of 3 to 10 years, probably varying by water heater type and model and anode rod properties as well.
American Water Heater Co. recommends that the water heater sacrificial anode rod should be removed from the water heater tank every three years for inspection, and if the rod is more than 50% depleted it should be replaced.
If the water heater is installed in an area where the water is hard, or "aggressive" or "corrosive", inspect the water heater after 3 years, or for Rheem water heaters, every 5 to 8 years.
Rheem Corporation, a manufacturer of water heaters, recommends that the water heater anode be inspected after 8 years (Rheemglas™, RheemPlus™) to 10 (Rheem Optima) years depending on the water heater model.
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How to Replace the Water Heater Anode Rod - step by step
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 On inspection, if your water heater sacrificial anode is corroded and pitted, or if the lower portion of it has dissolved completely, the anode needs to be replaced and you will need to shorten the interval at which you inspect this component.
It's a relatively small plumbing job to disconnect water pipes from the water heater and then pull and check, and replace the dip tube/sacrificial anode if necessary.
A great time to change the water heater dip tube or anode is when the water heater tank has been drained for some other reason, such as to de-scale or de-lime the water heater (as the worker is doing in our photo at left) - see WATER HEATER SCALE - De-Liming Procedure.
Safety Warning: do not attempt to de-lime or de-scale an electric water heater without first making sure that the de-scaling chemical won't contact the sacrificial anode - otherwise an explosion or fire could occur.
The water heater anode location, for purposes of removal or replacement on most water heaters is accessed from the water heater tank. In our sketch of a water heater showing the anode location, the anode (red arrow) is inserted into the water heater tank top at the spot pointed to by the green arrow. Usually this location is marked on the water heater top as "Anode".
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 Here are the detailed steps in replacing a water heater anode rod:
- The water heater is turned off.
- Turn off the cold water supply line that enters the water heater tank.
- Open a nearby hot water faucet to remove pressure from the water heater tank.
- Attach a garden hose to the water heater tank drain valve - found near the bottom of the water heater tank. Route the hose outdoors or to a convenient floor drain.
- You can route the hose to a nearby sink only if the height of the sink edge (over which the hose has to pass) is a couple of feet lower than the top of the water heater tank.
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A higher hose destination will prevent the water heater tank from draining. If your water heater drain valve happens to be high enough above the floor you can skip the hose hookup and just use a plastic pan or bucket as we show in our photo (below left).
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- Using the water heater drain valve we just described, drain five gallons of water out of the heater.
- Close the water heater drain valve.
- Remove the anode rod - you'll see on most newer water heaters that the anode rod is a separate device from the dip tube - so you won't have to disconnect the cold water supply piping. Instead take a look at the top of the water heater and you'll see a hexagonal head marked "Anode".
- Unscrew the rod and using teflon tape or pipe dope, screw in its replacement.
- Open the cold water supply to the water heater and check for leaks.
- Turn the water heater power back on.
Some water heaters do not have a sacrificial anode rod. Instead these water heaters may use a chemically inert anode rod to which electrical power is provided to achieve the same anti-corrosion function. Be sure to disconnect the anode rod electrical power before attempting water heater cleaning, and be sure to restore power after the tank is returned to operation.
Also see WATER HEATER FLUSH PROCEDURE where we describe the effects of a deteriorated plastic water heater dip tube. |
How Long Should A Water Heater Last?
See AGE of WATER HEATERS for the answer as well as for our list of factors that affect water heater life.
Frequently Asked Questions (FAQs)
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
- John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
 Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
- "The Fight Against Corrosion - A Study of the Nature of Corrosion and its Problems in Water Services and Heating Systems", Daniel Davies, Research and Development Services, Stansted Mountfichet, Essex, England, World Plumbing Conference-IV, "Plumbing and the World Environment, Compendium of Workshop Papers, October 3-6, 1996, Hyatt Regency Chicago, Chicago, IL", [personal correspondence, DJF - Author, July 2011]
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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