Water Heaters 101


Tank type Water Heaters

Ok, let’s start with the basics. Most water heaters you’ll run into are conventional storage type water heaters. They have a tank (typically between 10 and 80 gallons) where water is stored and kept heated by an electric heating element or plain old fire in the case of a gas or oil unit. The temperature of the water in the tank is kept within a set range by a thermostatic control. They are required to have a temperature and pressure relief valve that prevents dangerous pressure and heat buildup. Very simple and usually relatively inexpensive (compared to some of the other options) to purchase and install, tank type water heaters typically last 10 to 15 years, but depending on several factors this can vary widely (more on this later).

Every manufacturer has different guidelines but they all have recommendations for periodic maintenance. These usually include annual or semi-annual flushing of the tank and/or draining of a gallon or so monthly, periodic checks of the pressure temperature relief valve and regular checks of the anode rod/s (which help to prevent corrosion). Every manufacturer recommends keeping the tank and the area around it clean and clear of debris. Please keep in mind that tank type water heaters contain…. you guessed it – HOT water, making the danger of scalding very real. Most of the maintenance requires professional attention but it’s the only way to maximize the life of your equipment.

The most common cause of death for a tank type water heater is a leak caused by corrosion. Leaks from the external piping can usually be fixed, internal leaks from the tank cannot. Buildup of scale from minerals in the water can also be a source of trouble, such as an electric heating element being crusted over so badly that it won’t heat the water effectively any more. Other failures can be caused by malfunctions in the control systems or interruption in fuel or electric supply. Typically, a no hot water problem from a water heater that is in decent shape can be repaired, but as the unit gets older, repairs become less cost effective. Spending a few hundred dollars to repair a heater that’s seen 70% or 80% of its life is rarely worth it, especially when you add potential energy savings from a newer, more efficient unit.

When it’s time for replacement, the least expensive solution will almost always be a direct replacement of the identical water heater. Often though, you can’t get exactly the same model anymore or you can get a better quality and/or more efficient unit that’s close. The good news is that replacing a tank type water heater is something that a typical plumber does regularly, so making adjustments to the installation is all in a day’s work (it does get interesting sometimes though).

Since it has been our experience that pretty much no one does the recommended annual maintenance, we recommend having a comprehensive maintenance every three years, including replacement of the anode rod, a tank flush and inspection of the relief valve. While this may not be ideal, it is usually sufficient to significantly extend the life of your water heater, reduce your long term costs and reduce the likelihood of the headache of a tank failure. A tank type water heater that is maintained this way has a high probability of  beating the dismal average of 10 to 15 year lifespan, with many living to a healthy 30 plus years.

High Efficiency Water Heaters

  Changing over to a more efficient type of water heater can be a more expensive proposition, but energy savings and convenience considerations may well make it worth the expense. The tankless types of water heaters are more efficient because they don’t have to constantly re-heat water in the tank even when not in use. Modified venting and condensate drains allow for a cooler burning and more efficient unit in condensing type units. Tankless water heaters also typically last longer. Small on demand (or point of use) water heaters may also be used as auxiliary units for problem areas like a half bath way down at the end of the hall that takes forever to get hot water. Remember, the more expensive your energy source, the more an efficient system can save.

Beside the cost of the unit, changing the type of water heater you use often involves significant re-routing of pipes, moving control systems and gas or electric supply, and even drilling holes in the side of the house for venting. It’s not done on the cheap, but if you think return on investment at this level, especially when considered as part of a whole house solution, you can see big savings on energy usage. Also, most tankless units are relatively small wall hung devices that can save considerable space over tank type heaters (they’ve been real problem solvers for us when trying to maximize space for finished basements and such). There are even combi boilers that can heat your house and your domestic water in a single compact unit (or a number of them in tandem for a larger structure). Combi boilers (like in the photo on the left) are a modern and efficient way of providing a home with heat and hot water and can be found regularly in new construction where space efficiency and energy savings are key.

We don’t usually recommend electric tankless water heaters because of the high demands on the electrical system. These units require significantly more power over short periods of time than a tank type water heater which can heat the water much more slowly. The additional costs of electrical upgrades typically outweigh any gains brought by using less power over time.

Other Types of Water Heating

Less commonly domestic hot water is provided through a heat exchanger by the conventional boiler that heats the house. These systems come in several configurations, both on demand and with storage tanks. As you might imagine they can get quite complex (like wall hung combi boilers) and require experience and expertise to service. Like the systems mentioned earlier, failures can come through several different sources, including control system failure, corrosion, and mineral scale buildup. Failures of storage tanks due to corrosion (on the systems that have them) are very common.

Water quality issues

You may have noticed that corrosion and mineral scale are a common theme in the demise of water heaters. In fact, water quality is a huge factor in the lifespan of all of your plumbing. Acidic water is a real killer, it eats through pipes, valves and fixtures ravenously and is also not particularly good for your health. High mineral content is nearly as bad. Besides making your soaps and detergents ineffective, scale buildup can make a mess of your appliances and fixtures, as well as clog your pipes. Testing of well water is key to the life of your plumbing and your health.

Wrapping it up

The above is (I hope) a very simple overview of the common types of water heaters and some of the issues you may have with them. Please feel free to make comments below, and please ask any questions that you may have, whether on something in the article or something we may have omitted. If there is enough interest we may do a deeper dive into some of the particular systems, and we definitely plan to continue these plain language chats on plumbing, HVAC, and home improvement issues.

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