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AGE of WATER HEATERS
ALTERNATIVE HOT WATER SOURCES
ANODES & DIP TUBES on WATER HEATERS
ANTI SCALD VALVES
APPLIANCE DIAGNOSIS & REPAIR
APPLIANCE EFFICIENCY RATINGS
AQUASTAT CONTROL Functions
BACKDRAFTING HEATING EQUIPMENT
BACKFLOW PREVENTER, HEATER WATER FEEDER
CARBON MONOXIDE - CO
CHECK VALVES, WATER SUPPLY
CLOGGED SUPPLY PIPING
CROSS CONNECTIONS, PLUMBING
DEBRIS in WATER SUPPLY, Water Heater
DRAIN a WATER HEATER TANK
ELECTRIC WATER HEATERS
FLOODED WATER HEATER REPAIR
FREEZE-PROOF A BUILDING
GALVANIC SCALE & METAL CORROSION
GAS BURNER Flame & Noise Defects
GAS FIRED WATER HEATERS
GAS PIPING, VALVES, CONTROLS
HEATING COST SAVINGS METHODS
HOT WATER SUPPLY
HOT WATER IMPROVEMENTS
HOT WATER DELIVERY SPEED UP
HOT WATER EFFICIENCY IMPROVEMENT
HOT WATER PRESSURE EXPANSION RATE
HOT WATER PRESSURE LOSS
HOT WATER PROBLEM DIAGNOSIS
HOT WATER QUANTITY IMPROVEMENT
HYDROGEN SULFIDE GAS
INDIRECT FIRED WATER HEATERS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
NO HEAT - NO HOT WATER: HEATER DIAGNOSIS
NOISE, WATER HEATER
ODORS IN WATER
PIPING IN buildings, Clogs Leaks Types
RELIEF VALVE LEAKS
RELIEF VALVES - Water Heaters
SCALE REMOVAL, WATER HEATERS
SEWER GAS ODORS
SOLAR HOT WATER HEATERS
TANKLESS WATER HEATERS
THERMAL EXPANSION of HOT WATER
THERMOSTATS, WATER HEATER
TIMERS for ELECTRIC WATER HEATERS
WATER HEATER ALTERNATIVES
WATER HEATER ANODES, DIP TUBES
WATER HEATER AIR INLET
WATER HEATER DEBRIS FLUSH
WATER HEATER DRAIN PROCEDURE
WATER HEATER EFFICIENCY
WATER HEATER FLUSH PROCEDURE
WATER HEATER NOISES
WATER HEATER PROBLEM DIAGNOSIS
WATER HEATER COMPARISONS, PROPERTIES
WATER HEATER SCALE
WATER HEATER SAFETY
WATER HEATERS for HOME HEATING USE?
WATER ODORS, CAUSE CURE
WATER PIPES, Clogs Leaks Types
WATER PRESSURE TOO HIGH: DANGERS
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER QUANTITY IMPROVEMENT
WATER SOFTENERS & CONDITIONERS
WINTERIZE A BUILDING
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.
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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. This article describes the diagnosis and cure of debris in the building water supply traced to a deteriorated water heater dip tube/anode.
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:
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
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.
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
How Often Should the Water Heater Sacrificial Anode be Inspected?
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.
How to Replace the Water Heater Anode Rod - step by step
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".
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).
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.
Also see WATER HEATER DEBRIS FLUSH
But if both cold water pressure/flow and hot water pressure/flow are slow or inadequate, readers should see WATER PRESSURE LOSS DIAGNOSIS & REPAIR.
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Frequently Asked Questions (FAQs)
(June 28, 2014) Amy Prue said:
I have blackish water coming out of all faucets on a well hot and cold water. There seems to be some sediment in the water but not much. And has a kind of has a slimy texture. It also seems to come and go when running water. (being black more then clear)
Amy, check your water for sulfur or other contaminants before changing equipment, but also investigate for a deteriorated sacrificial anode in a water heater tank.
Questions & answers or comments about water heater anodes & dip tubes: water heater odors, corrosion, leaks, & tepid hot water troubleshooting.
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