When it comes to keeping your showers warm or your dishes and clothes clean, a reliable and efficient water heater is essential for any home. With so many different types of water heaters on the market, choosing the correct one for your home can feel overwhelming. This guide will provide you with an introduction to the different types of water heaters so you can make an informed decision for your home.
Tank Type Water Heaters
Tank type water heaters are the simplest and most flexible water heater type. No matter what fuel source, vent, or space you have available, there will be a tank type water heater to fit your needs. Tank type water heaters can utilize oil, natural gas, propane gas, or electricity to heat the water. They also come in different sizes typically ranging from 30 gal capacity to 100 gal capacity. Tanks should be sized based upon peak demand for the house. Multiple tanks can also be piped together to increase the capacity as well as add an extra level of reliability. Both tanks rarely fail at the same time, meaning one tank can be shut off and isolated while the other continues to provide hot water to the house, although the capacity will be diminished. While most gas and oil versions are atmospherically vented into a chimney, power vented models are available if the chimney is no longer operable or is going to be removed. The power vent utilizes a fan assembly and piping to force the combusted materials to the outside of the house.
While they are the most versatile, they are also the least efficient and usually have the shortest life spans. The gas and oil fired water heaters lose their efficiency because they require a vent to exhaust the byproducts of combustion. This allows stack effect to continuously pull heat up the chimney, lowering the temperature of the water and causing the unit to fire more frequently. Electric water heaters derive the inefficiency from the resistive elements that are used to heat the water. The elements are essentially resistors that get red hot due to the difficulty the electricity has moving through them. Hybrid electric water heaters are a newer product designed to increase the efficiency of electric water heaters. Hybrid electric water heaters are electric water heaters that incorporate a heat pump system to the tank. While the heat pump is super efficient, it has a slow recovery rate and will sometimes need to rely on the electric elements to keep up with demand.
The life span of tank type water heaters can vary widely, but usually fall between 5-15 years. The electric models typically last longer due to the decreased stress on the tank. Gas and oil fired models heat the bottom of the tank, creating expansion and contraction that damages the glass lining faster, while the electric elements are submerged in the water and heat it directly. Water quality and usage also play a role in how quickly the tank will fail. Most tanks come with a sacrificial anode rod that can be replaced periodically to extend the life of the tank.
Tank type water heaters are a great solution for any home water heating needs. They have the versatility to handle any situation and will produce hot water reliably for the entirety of their life span.
On Demand Water Heaters (Tankless)
On demand water heaters are highly efficient and produce endless amounts of hot water. There are two types of tankless water heaters. The older version is a coil of copper tubing that is submerged inside a boiler. The boiler maintains temperature throughout the year and transfers the heat to the domestic water as it passes through the coil. The modern version, and the more efficient version, are the self contained units that hang on the wall.
Tankless coils that are submerged in a boiler are effective, but require safety mixing valves to be installed on the outlet piping. If a mixing valve is not installed, there could be instances where 180 degree water comes out of the faucet. The effiency of these systems suffers because they rely on a boiler to maintain water temperature. The boiler typically is a cast iron boiler that utilizes a chimney, leading to heat loss and more frequent firing. When working properly, the coil produces endless hot water, but over time the coil gets coated with scale and the heat does not transfer fast enough to maintain temperature. The tankless system is very simple and usually needs no maintenance. Generally these are not being installed new but can be replaced to avoid the major cost of installing a new system.
On demand hot water heaters have high efficiency because water is only heated as it passes through the heat exchanger. This means there is no standby heat loss from maintaining temperature in a large volume of water. These units usually only utilize natural gas or propane gas to heat the water. While electric on demand water heaters exist, the cold temperatures of Massachusetts make the power requirements too high for most homes. In order to get a high enough flow rate for use in the winter, the electric units need close to 100 amps of power (some older homes only have 100 amps coming to the house total). The gas fueled units can take up to 199,000 BTU operate properly. This means that a new gas line may need to be run if you are replacing an older tank type water heater. They also require an exhaust and air intake pipe to be run to the exterior of the house. Often the easiest route is out the side of the house, but there are kits that allow an old chimney to be used as a chase to run the exhaust and intake pipes in. An old chimney flue cannot be used for the exhaust gasses from the on demand water heater. Because they modulate, the stack temperatures are low, creating condensation and acidity that will cause the chimney liner to fail prematurely. The largest on demand water heaters have high enough flow rates to run multiple fixtures at the same time. They can also be piped together to increase flow rate capacity for cases of exceptional demand. On demand water heaters are also supposed to be serviced every 1-2 years to maintain optimal efficiency and increase life span. The life span of on demand water heaters vary greatly, but usually fall somewhere between 7-15 years.
On demand systems provide the pinnacle of comfort due to the endless hot water they produce. These systems are perfect for those with large hot water demands.
Indirect Water Heaters
Indirect water heaters utilize a boiler to heat the water and pump it through a zone connected to the tank. Unlike tankless coils, these tanks can be used with new high efficiency boilers making them super efficient.
Indirect water heaters look similar to a tank type water heater, but there are major differences. The indirect tank is heated by a independent zone off a boiler. When the tank calls for heat, the boiler fires and pumps the heated water through a coil in the indirect water heater transferring the heat to the domestic water. The tanks retain the heat very effectively because they do not have a flue to pull the heat off the water and are completely encapsulated with insulation. The low heat loss and high recovery rate due to the high BTU input of the boiler results in near endless amounts of hot water. Similar to the submerged tankless coil, it is recommended to install a mixing valve in the outlet piping to ensure a consistent hot water temperature.
Unlike tank type water heaters, indirect water heaters are constructed of stainless steel. Many indirect water heaters come with lifetime warranties for the original installing homeowner. Unfortunately these warranties are not transferrable, but it is not uncommon to find indirect water heaters that last for 15-20 years.
While indirect water heaters can only be utilized in situations with a boiler, their long life span and high efficiency make them a great choice for any home with a boiler.
Summary
Choosing the right water heater is important for maximizing comfort and health in your home. In this article we have explored the different types of water heaters to help you choose the correct one for your situation.
Tank type water heaters are the most versatile, but the least efficient with the shortest lifespan.
On demand water heaters have the highest efficiency and comfort, but are the most maintenance heavy.
Indirect water heaters have high efficiency, no maintenance, and the longest life spans.
If you still have questions about which system is best for your situation, feel free to contact us by phone at (508) 233-2382 or through the email form on our website.