The best water heater is a 6-year-warranty tank with the maximum amount of insulation you can get and a few extra parts.

In some cases, R-24 insulation is available, but the least expensive tanks typically have about R-6. This is a place you can save money year after year, just by choosing wisely. (Since we created this page, things have become more complicated. Click here, read up, and then come back.)

The tank should have a hex-head, magnesium anode rod in its own threaded port. That means there is room in the hot-outlet port for a second, combination anode/hot-water outlet/plastic-lined nipple (that's one of those extra parts).

You install it simply by screwing it in. That will give you the equivalent of a 12-year-warranty tank for a lot less money. Maybe better than 12-year.

Which brands fall into this category? All tanks of Rheem and its sub-brands: Ruud/Richmond/GE. Some heaters made by A.O. Smith and Bradford White. And some of Smith's subsidiary, State.

However, things have gotten more convoluted in the past few years.

For one thing, long about 2005, Rheem changed its design, with a deeper hot port that extends well below the threads, with the result that a standard combo anode won't go in without drilling out the port and may not allow water to pass even after that. Most people aren't too keen to drill near the threads, so we offer a special combo rod that will work in this new design, but it's about $6 more for a .75-inch diameter rod, as opposed to the .84-inch-diameter anode that works in everybody else's heaters. The .84-inch has 25 percent more sacrificial metal than the .75-inch.

At the same time, there are some other issues with Rheem. Several years ago, the federal government mandated a flame-arrest system on all water heaters to keep them from igniting flammables used or spilled nearby. Rheem's design uses a piece of glass that breaks if the systems activates. But once the glass breaks, whether by intention or accident, the tank no longer functions and has to be replaced. Other systems use a metal strip that melts and can be replaced. Rheem is good about replacing them under warranty, but it's still an inconvenience.

And Rheem has always used an anode with a resistor in it to slow down its reaction with the tank and sometimes that causes it to "passivate," sort of go to sleep. This is more likely to happen in naturally soft water, such as from the mountains. Where two regular magnesium anodes would work in unison, the resistor rod may doze while the more reactive standard anode we provide is consumed, then kick in. Or passivate altogether. Also, Rheem won't say how much insulation its tanks have, either by R factor or by inches, leaving you to guess at Energy Factor numbers.

Then there is American/Whirlpool. Our only grump with its water heaters is that they always come with aluminum anodes, which we don't like. But they offer one model with three inches of insulation, equivalent of R-24. That's a good thing. And they usually have a hex anode in its own port. Tradeoffs.

State uses aluminum anodes in all its heaters as of this writing (February 2008) except its Premier line, which has magnesium. Many State tanks also have combo anodes in the hot port instead of a hex anode in its own port.

A.O. Smith, which owns both State and American, makes tanks with both hex anodes in their own port, and combo rods in the hot port, with no room for a second one. They can be either aluminum or magnesium. So if you can get someone to order you a Smith with a hex magnesium anode, that would fit our preferences.

Bradford White has always used magnesium anodes, but for years, its models were always combo-rod heaters. Recently, it started offering a tank with a hex anode in its own port, which pleases us. BW only markets through contractors, so you can't just go out and buy one and do it yourself.

And finally, if you have odor problems, putting two aluminum/zinc anodes into your tank isn't a good idea since it provides more metal for the bacteria that cause the smell to react with and may increase the amount of odor. Stick with just one and keep an eye on it.

So there you have it. These are the issues, from our point of view, of the ins and outs of longevity and energy efficiency. There may be other factors you want to take into consideration when making a choice, not least of what is available where you live. Then you have to add those with these and come to a decision.

Anyway, how do you tell the right configuration? Well for starters, can you see a hex-head anode on top of the tank? If not, there may only be one anode in the heater, in the hot-outlet port. In that case, there's no place to put a second one and double the tank's rust protection. A couple of companies employ this arrangement. Don't buy that kind of tank.

Anyway, this tank was a Rheem. You can see the hex nut in the middle upper part of the photo. It's flat. Even though it's flat, we know Rheem uses magnesium anodes.

But for other brands, look for a bump on the hex head, as in the photo at right. The lefthand anode is aluminum; the righthand one is magnesium.

Also, we want to say that all this has nothing to do with tank quality. Other brands may be just as good in that regard, but this configuration enables the longest life and efficient control of sediment.

Speaking of sediment, if you're in a hard-water area, you'll want to add a flush kit so that you can effectively expel that from the tank. Otherwise, it builds up and harms the tank, makes noise and reduces the volume of hot water available.

The old tube sits in the cold port. That's the position with the blue-topped pipe nipple. Ordinarily on a new tank, there won't be a nipple. If there is, you'll need to remove it with a wrench. Underneath it is the dip tube.

Often, you can simply reach in with your little finger and work it out with a circular motion. It usually has a flared top that sits on a metal ring in the port. A wooden dowel works, too, as does one handle of a pair of pliers. That metal ring has to be drilled out.

For that, you need a drill and a 7/8-inch hole saw bit, like the one at right. It takes all of about 30 seconds to drill out the ring. Then the dip tube screws into the port in the same way as the anode did. Remember: six wraps of tape.

Also, note that the inside of the dip tube has a mark. It indicates the direction of the curve, which you won't be able to see when you start screwing it in. The curve, at the last, should point in the opposite direction from the drain valve, but not toward the flue, if there is one, so that it will swirl the water.

The next thing to do involves replacing the standard drain valve with the ball-valve drain. Most water heaters either have the "cone valve," upper left, or the faucet type, lower left. A few have brass spigots. The cone valve is removed by turning four turns counterclockwise while pulling slightly, then turning clockwise until it comes off. It's usually screwed on to a metal nipple, which you can use in place of that which comes with the flush kit.

The faucet type has to be completely removed. Use a wrench or pliers and take a grip as close to the tank as possible and gently turn. On new tanks, the plastic hasn't had a chance to become brittle and usually the valve will come out easily. There is a slight chance of breakage. In that case, you can easily tap out the plastic still in the threads with a hammer and flat-bladed screwdriver. Place the blade on the lower edge of the remaining plastic and tap gently.

In rare cases, it may be hard to screw the anode into the tank. In those cases, there is a lip of the glass lining that must be drilled out, again with the hole saw. It involves placing the blade of the saw below the threads in the port and angling it slightly, then drilling briefly. Do that three times, in thirds of the port. Then the anode should easily screw in.

All this that we've described takes a whole lot less time to do than to describe. A minute for the anode and maybe five minutes for the flush kit.

All water heaters, including tankless ones, have some standby heat losses. Tank heaters lose heat through the walls of the tank and up the flue. Serious losses for all types of heaters, unless they are right next to the outlet being used, is, from the piping. That runs from the heater to the faucets. It's made of copper, mostly, sometimes steel. It radiates heat very well.

So if you want to cut standby losses, insulate the pipes, if you can, and when you install a tank heater, make heat traps out of copper flex lines. How? Use a longer flex than you need and make a big gooseneck in it, like a question mark. Heat will rise up the flex to the top of the gooseneck and no farther. The photo at left is of a commercial water heater, but the principle is the same. Heat will rise as far as the red lines, but not go into the blue because heat only rises. So insulating to a little beyond the top of the rise will be effective.