Guide to Hot Water Heater Anodes & Dip Tubes - Inspection, Diagnosis, & Repair
InspectAPedia^®  -    

• 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
• How to choose among types of hot water heaters
• Guide to inspection of electric water heaters
• No Hot water? how to get more hot water flow, quantity, performance from your water heater

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. By constructing the dip tube of a metal which is more readily corroded than the steel of a steel hot water tank, the anode protects the hot water tank from early failure due to corrosion.

Here Carson Dunlop's sketch shows the location of the sacrificial anode 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 other water heaters send cold water into the water heater tank from the tank top, down through a "dip tube" that may also serve as the sacrificial anode.

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.

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.

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.

Procedure to inspect a water heater Sacrificial Anode or Dip Tube

In our photo (left) our pencil is pointing to the water heater 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.

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

• 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?

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.

If the water heater is installed in an area where the water is hard, inspect the water heater after 5 to 8 years.

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.

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 Procedures.

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.

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.

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.

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