Water heater anode rod replacement

A glass-lined steel tank is never a perfect coating. The anode is a rod of a more reactive metal screwed into the tank so that it corrodes instead of the steel at every flaw in the lining. Rheem's manual puts it plainly: the rod "is slowly consumed, thereby eliminating or minimizing corrosion of the glass lined tank." A.O. Smith gives the other half: once the rod is depleted, the tank starts to corrode and eventually leaks.

That is the whole case for checking it. The rod is a consumable; the tank is not. Most rods hang from a hex-head port in the top. Bradford White's gas heaters combine the rod with the hot outlet nipple instead, and some heaters carry two rods, both of which need inspection.

There is no single industry interval, and the manuals do not agree. Quote the one on the rating plate, not a rule of thumb.

The sequence is the same on every tank: energy off, pressure off, enough water out, rod out. The details below are lifted from the manufacturers' own procedures. Where they differ, the difference is named.

1. 1

   Kill the energy first

   Electric: breaker off. Gas: gas control to off. Rheem's manual says to shut the gas at the manual shut-off valve before draining any water. On a heater that plugs in, Bradford White's service procedure also unplugs it.

2. 2

   Cool it, close the cold, relieve the pressure

   A.O. Smith runs the hot water until it is cool, turns the cold supply off, then opens a hot faucet to depressurize the tank. Rheem says the cold supply must be off before the rod comes out. Nothing gets unscrewed on a tank still at line pressure.

3. 3

   Drop the level only as far as the job needs

   A.O. Smith's commercial manual drains about 5 gallons before the rod comes out. Bradford White's combination rod lives in the hot outlet nipple, so its procedure drains below the outlet connection and disconnects the nipple from the piping before the rod can turn.

4. 4

   Expose the hex and break it loose

   On A.O. Smith residential electrics the rod sits under a black plastic cover marked "Anode", with foam to cut away. The manual calls for a 1-1/16" socket with an extension. A Bradford White service manual for its condensing power-vent series puts its hex head about 4-1/4" below the jacket head and calls for a deep 1-1/16" socket.

   Do not assume every head matches: Corro-Protec sells its install kit with both 1-1/16" and 1-3/16" sockets. For a seized rod, their guide suggests a breaker bar, impact wrench or torque multiplier.

5. 5

   Check the ceiling before you pull

   A sacrificial rod is long, and a water heater under a low ceiling or a shelf may not have room to lift it straight out. Corro-Protec's guide says the old rod can be cut into sections on the way out, holding the bottom piece so it does not drop into the tank. For the new one, a segmented or flexible rod goes in a link at a time. Match the thread and the length of the rod you took out.

6. 6

   Inspect, then reinstall or replace

   Hold it against the replacement criteria below. Thread sealant tape or pipe joint compound on the threads (A.O. Smith); plumber's tape (Bradford White). Tighten it down; A.O. Smith says it is not necessary to replace the foam you cut.

7. 7

   Refill before the power goes back on

   Cold supply on, hot faucet open until it runs full to purge the air, then check the fitting for leaks. A.O. Smith warns not to restore power to an electric heater unless the tank is completely full: a dry element burns out. Gas units relight from the lighting label.

The manuals give two explanations for hot water that smells of rotten eggs. Rheem says water with high sulfate or mineral content can react with the cathodic protection process to produce hydrogen sulfide, and that chlorinating the supply should minimize it. A.O. Smith blames harmless bacteria that multiply in the tank, and calls chlorination the only sure treatment.

The rod swap is the lesser fix. A.O. Smith says a special zinc anode may help reduce or eliminate the odour, and its commercial manual warns a special rod may reduce but not eliminate it. Bradford White points the owner to an alternative anode from the installing supplier, plus a flush with dissolvers to kill the bacteria. A.O. Smith also allows raising the tank to 140°F, with mixing valves at the fixtures because anything over 120°F raises the scald risk.

Softened water is the other rod-killer. A.O. Smith's commercial manual calls artificially softened water exceedingly corrosive and requires a yearly inspection with it. Bradford White says softened or phosphate-treated water needs more frequent checks. If you are quoting a water softener installation, put an anode check on the same ticket.

The rod itself is never a warranty part. A.O. Smith and Bradford White both exclude anode rods as consumables, and Bradford White's warranty also excludes odours and rusty water. What the warranty does reward is maintenance: A.O. Smith covers a heater only when it has been installed, operated and maintained per its printed instructions. Write the inspection date and the rod's condition on the invoice and on a tag at the heater. The water heater brands comparison sets the two makers' full tank terms side by side.

A powered anode costs more up front. One maker's list prices ran $169.95–$199.95 by tank size and port (read 2026-10-18), and it needs an outlet. A.O. Smith offers its own powered anode on some models. For a third-party rod on a heater still under warranty, get the heater maker's position in writing first.

Outside warranty, price the swap against the whole job. The water heater replacement cost guide has the installed bands, and the water heater cost calculator builds one from your own inputs. If the customer is replacing anyway, weigh tank vs tankless and run the water heater sizing calculator before ordering. Closed systems also need the expansion tank checked.