Sometimes you'll find a pipe nipple at the top of the anode instead of a hex head. This combination anode is in the hot water outlet at the top of the tank. You'll be able to determine if it's this type by disconnecting the hot side plumbing and poking a long, stiff wire down into the pipe nipple. If it stops firmly two to six inches in, you have found the anode (or one of the anodes). If not, the anode is hiding elsewhere.
Better tanks may have two anodes. The main (if not only) physical difference between five and ten year warranted tanks is the addition of a second anode. The cost of a ten year tank is many times what it would cost you to replace the second anode yourself. If your tank is hard to work on, consider installing two anodes so that you won't need to deal with it again any time soon.
Aluminum and magnesium are the most common metals formed around an anode's steel core wire. You can tell the difference between them by bending. Aluminum is soft and bends easily, while magnesium is springy and more resistant. (We replace aluminum anodes whenever found because aluminum many be a contributing factor in Alzheimer's disease. Until aluminum is proven innocent, we believe it is safer to avoid using aluminum rods.)
If rotten-egg (sulphur) odor is a problem, a zinc/aluminum anode is available. In combination with other methods, zinc rods help eliminate this odor problem.
If you have limited overhead clearance, you may want to use a flexible link-type anode as your replacement. Flex-rods are segmented so they can be bent for easy installation.
Where can you get a replacement anode? Plumbers rarely have anodes in stock, but they may be able to obtain them from plumbing supply houses. We get ours from Gull Industries in San Jose, California (1800-7486286); you can too. A resource of last resort, because of generally higher cost, is the water heater manufacturer. Anodes should run around $18-$30, depending on the type needed.
Before unscrewing anything, turn off the power. If gas, turn the heater to the pilot position, so you won't need to relight the pilot. Turn off the cold water supply to the heater. Attach a hose and open the drain to relieve pressure. Leave the drain open so pressure cannot build up.
If you have a hot outlet type anode, all you'll need is a pipe wrench to unscrew and replace it. The hex plug type will need a 1 1/16 inch socket, a strong wrench and a cheater bar. For really entrenched anodes, use a six-point instead of a twelve-point socket. It won't round off the corners of the hex plug. (Anodes can be a real trail to remove. Professionals use an expensive tool called a torque multiplier. It trades speed for force and triples the available torque. If your anode absolutely won't come out, you can leave it in place and add a hot outlet type anode.)
As you unscrew the anode, listen closely for the sound of air being sucked into the tank. You want to hear that hiss to make sure the tank is not under pressure. If the tank were still pressurized, the loosened anode could take off like a rocket. So if water seeps from around the threads as you unscrew the anode, stop and relieve that pressure. A faulty cold water shut-off may allow leakage into the tank, or the drain may be clogged.
Inspect the Anode
Normally, if six inches or more of the core wire is showing, it's time to replace your anode. If you find the
anode is aluminum instead of magnesium replace it even if no core wire is showing (see above).
Inspecting the anode will give you information about the condition of your tank. If there is still some sacrificial metal left on the core, your tank is probably in acceptable shape. In general, the less core wire exposed, the better protected your tank.
One condition which can mislead you is anode passivity. You will see much sacrificial metal left and believe your tank is being protected. In actuality, the metal is covered with a hard, dense coating which prevents further sacrificial action. Test for this by bending the rod. If flakes of scale crackle off, the rod has passivated and needs replacement.
Should you find only a bare wire or less, rusting has begun inside the tank (see Anode Deterioration diagram). Examine the tank's exterior (at fitting penetrations, in the combustion chamber and flue). If there is no external evidence of rusting, anode replacement is likely a good bet.
Overhead clearance can be a concern when you replace your anode. If the anode misses fitting into the tank by just a little, it's possible to bend the rod at its center, slip it half way in, and then straighten it against the opening and slide it the rest of the way in. When doing this, check for straightness by tilting the rod when it's about half way into the tank so its lower end touches the tank wall. Then rotate it and see if the top wobbles. If it does, a little tuning is needed. The anode must be straight enough so it can be screwed in without touching anything in the tank.
If you have a gas heater and if the vent goes straight up, you may.be able to slip the anode up the vent and then down into the heater without any bending at all.
If you have less than about 2 1/2 feet overhead, use a segmented anode to prevent frustration. These anodes are bent at the joints and straightened as they're inserted into the tank. In worst case, if you have no other choice, you can drain the tank, disconnect it, and tip it enough to insert the new anode.
Use plenty of teflon tape to seal the threads of whichever anode you use. This will ensure easy removal the next time.
Check the anodes every three to four years. If you have very hard, acidic or softened water, check it in one or two years. Also, if the old anode was long gone, check the new one when it's a year old to determine how fast it's being used up. Keep a record on the side of the tank showing what you did and when. It will help remind you when to have another look.
Our experience suggests that water heaters will last as long as you're willing to maintain them. You may already have the last water heater you'll ever buy.
Larry & Suzanne Weingarten, PO Box 928, Monterey, CA 93942. Phone/Fax 408-394-7077
Replacement anodes: Gull Industries, San Jose, CA, 800-748-6286 iti
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