Here, we’ll take a look at some of the many things that have been invented or adapted to hot water heaters over the past century or so.
Note that most of these advances apply to tank models, as tankless and alternative energy models are currently in a state of rapid development that makes it hard to pick out specific innovations before something else surpasses them.
Related: Water Heater History
Water Heater Innovations
Anode Rods (Sacrificial)
One of the most important parts your tank can have, an anode rod is a small metal cylinder that attracts corrosive materials found in water. The materials slowly eat away at the rod instead of the metal components of your water tank.
Magnesium rods tend to be the most common. However, people suffering from hard water or sulfuric smelling water should invest in a zinc rod.
You should check the condition of your rods once every 1-2 years and replace if the steel core is exposed or there’s too much calcium buildup to see the rod, although the average rod can last for 4-5 years under normal conditions.
Replacement rods are relatively inexpensive and require very little skill to replace, making them one of the best investments one can make. Note that some tanks have dual rods to further improve performance.
It should be noted that pure aluminum rods were common in older tanks, but the toxicity causes as it degrades make them undesirable. To check if your tank had an aluminum rod, simply try bending the rod. Aluminum will bend, unlike other rod materials.
Be sure to replace any aluminum rods with a safer material. Note that zinc rods are actually a blend of 1 part zinc to 10 parts aluminum and are generally considered safe for use.
A less-used innovation, combination anodes are a secondary anode that’s installed in the hot water outlet pipe. These are difficult to remove, generally requiring you to break the pipe, but they provide a second line of defense for metal pipe systems.
While it seems like a no-brainer today, the use of foam for insulation is a fairly recent innovation. State Water Heaters was the first to add foam insulation between the tank jacket and lining in 1979.
After a lot of facepalming, other companies quickly adopted this innovation and it has become a valuable standard in today’s industry.
The credit for this innovation generally goes to A.O. Smith in 1936, although other companies have developed their own versions over the years. Due to the corrosive nature of water, metal tanks wouldn’t last very long on their own.
By adding a glass inner lining, the metal has an effective barrier to reduce the risk of corrosion. Glass and glass-based coatings also have the advantage of being natural insulators.
The lining wears down over time, but does an excellent job of making even the least sophisticated tanks last at least six years.
While glass lining has been around since 1936, its use as the basis for more efficient linings cannot be understated. This is perhaps no more apparent than Rheemglas.
In 1954, Rheem technicians developed a porcelain lining that bonded to the inner tank surface. The life-extending quality of this new insulating technology took the industry by storm, and further development has led to today’s famously trademarked Rheemglas technology, as well as the use of porcelain linings being one of the industry standards.
Gas water heaters (see also ‘Hot Water Heater Vent Pipe Size‘) produce toxic emissions that must be vented through a flu system. However, even properly installed common vents can develop problems because they rely on convection (i.e. hot air rising through the vertical flu).
Powered vents use a blower to cool the exhaust and push it horizontally to wall-mounted vents. The cooling allows the use of PVC instead of metal for the pipes, further adding to the efficiency and longevity of this venting system.
While it does require electricity, there’s no risk of backdrafts or heavy reliance on potentially leaky metal ductwork.
Powered Anode Rods (Non-Sacrificial)
Reinventing the wheel can be tough, but that’s precisely what powered anodes do. These rods send out electrical pulses, scattering harmful electrons.
Powered anode rods last for six or more years and won’t degrade. They can eliminate severe sulfur smells and perform all of the tasks of a normal anode rod with ease.
The upside to this is the lifespan in harsh conditions, but they cost a lot more than a regular anode and require electricity to run.
This makes them extremely useful in locations with very hard water (see also ‘Hard Water Treatment‘) or high mineral content but unnecessary in homes with normal or pre-treated water. Corro-Protec is the industry leader when it comes to powered anode rods.
A special dip tube (see also ‘Water Heater Dip Tube Explained‘) stirs the water at the bottom of the tank, preventing sediment from settling. This sediment is piped out whenever you turn on the hot water, reducing buildup at the bottom of the tank.
This system works best in a home that uses on-demand heaters for the kitchen and preferably has softeners for the bathroom outlets to reduce the effects of hard water on the skin.
Solar Powered Heating
Long-term fans of Mother Earth News Almanac and other off-the-grid or eco-friendly periodicals may well be aware of solar-powered heating.
The most basic form uses black water-filled pipes in a glass-covered box. Sunlight heats the box, causing convection and the resulting hot water heats the walls of your home as it cools. But this is usually a closed system and thus cannot provide usable water.
Advances in solar cell (AKA photovoltaic or PV) technology have provided a couple new options. Solar cells can be used for heating swimming pools and may divert power in home use to fuel an electric tank or tankless water heater.
This isn’t the most efficient method, as producing power still requires plenty of sunlight and you’re not as likely to store enough charge to outlast cloudy days and nighttime requirements when diverting power to hot water production.
But what about the closed system we mentioned earlier? Well it turns out, you CAN use a more modern version of the rooftop box-based heating system to create an open system for hot water.
Heating is something the sun can do even in winter, and modern solar water heaters have both active and passive variations.
Despite being one of the oldest methods of heating water, modern solar systems have only been around since the 1980s and the recent push for LEED and other economic tax incentives have led to a huge push for developing this option in the last 20 years.
As a result, the potential for solar to become the standard water heating method in the next few decades is looking ever brighter.
Tankless and On-Demand
Technology has certainly come a long way over the decades, and the tankless water heater may well be one of the most impressive innovations. Tankless water heaters take up less space and heat water as it’s needed, providing a space and budget friendly alternative to the classic tank design.
They have long lifespans, an essentially unlimited supply of hot water (running too many taps at once can still use more water than the heater can provide per minute), and require less maintenance.
While the terms “tankless” and “on-demand” are synonymous, the latter term is more often associated in common conversation with smaller units, such as those used for the kitchen in an RV or to provide for a single room in the home, while the former term is more often associated with whole-home water heating.
While not ideal for every situation, it’s pretty easy to compare tank and tankless heaters to see which is best for you.