Each commercial manufacturer of water heaters puts in their own amount of anodes inside a water heater. The amount is usually based on warranty duration, hence the more anodes in a water heater, the longer the warranty the manufacturer will provide. Most manufacturers intentionally provide shorter warranties unless specifically asked for a longer one. Also, most consumers don't know enough about water heaters (who would spend a lot of time learning about them unless you're in the business) to ask about warranties and anodes so they don't ask in the first place. Also, the fewer anodes installed, the more likely the water heater will malfunction and the more likely you will buy a new one.
Money is the reason to install a commercial water heater that is a tank-type heater. It costs less for the tank-type water heater, but installing multiple tankless water heaters, especially in establishments such as hotels and restaurants, could be extremely expensive. Going to a tankless water heater system initially costs more money. Households are slightly more likely to go to a tankless water heater system, but again the same problem occurs: money.
Nonetheless in the next thirty to fifty years, virtually all water heaters will be tankless water heaters in the United States. It should be noted that most water heaters in Europe and Japan are already tankless water heaters. The tankless water heater industry has great momentum for new customers in the United States. The average anode rod lasts ten years. Some places in the United States, anode rods won't last much longer than two to four years! Some places last twenty to thirty years or longer.
This is all due to water quality in the area. If the water is too hard then people put salt in the water to soften it. This salt is more dangerous to an anode rod than the hard minerals it replaces.
This will cause the anode rod to fail. If the water is too soft, which means that too much salt naturally appears in the water, then the anode rod will have the same problems. It's not a situation that you have any control over.
Water has to be softened and anode rods need to be replaced. It's the only way. The water heater industry can make commercial water heaters with up to 4 anode rods. These 4 rod water heaters are uncommon but they should come with an outstanding warranty. The more anode rods that appear inside a water heater tank, the more lengthy the warranty. A plumber should replace anode rods since they are extremely difficult to change out and most times the water heater is stuffed in a utility closet with no overhead clearance from which to gain enough room to pull the water heater out and therefore the water heater must be partially disconnected to the plumbing and partially drained and tipped forward just to be able to remove it.
What a pain filled experience it can be. Its best to hire a plumber to do it.
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