Problems with a Tankless Hot Water Heater

Owning a tankless hot water heater has many benefits. The most obvious, of course, is that you will never again run out of hot water. You can take shower after shower or fill multiple bathtubs full of hot water and never run out. Tankless water heaters also save space and, in most cases, are much more energy efficient than a typical tank heater, which is constantly running. There are, however, a few drawbacks to purchasing a tankless unit that you should know about before making your decision on the type of water heater to purchase.

The Facts

Tankless water heaters are available in electric and propane-fired models, but the natural gas units are probably the most popular. These heaters use computer boards and sensors to monitor the flow of water and change the firing rate to provide the exact amount of hot water needed at any given time. They are extremely efficient and use no more than the amount of gas needed to heat whatever source of water you are currently using. Quite simply, the more hot water you use, the more gas is burned.

Function

Tankless water heaters are limited in the amount of hot water they can distribute at any one time. In most homes, where an average amount of hot water is needed daily this will not be a problem, but with larger families where several outlets may be in use at once, a lack of enough hot water may be a problem. Tankless units are also more expensive to purchase and install, and if you are looking for a unit that will support the needs of larger, 3 1/2+ bathroom homes, then be prepared to pay a larger price.

Considerations

There are very few electric tankless water heaters on the market today that will support the capacity needed for use in larger homes. They are ideal for smaller, one-bathroom houses or apartments where gas is not available, but for larger families that use an above-average amount of water each day, it may not be a good choice. In these instances, the tankless water heater may not be able to produce enough hot water. Additionally, a larger electrical service may be required to operate them, so that may require extra work to install the unit.

Misconceptions

With all tankless hot water heaters, you will experience what is known as "lag time." Lag time is the amount of time it takes from when a source of water is turned on until the water actually reaches the faucet. Even units that are marketed using the term "instantaneous" will still experience lag time. The time it takes for the water to travel through the many feet of piping to reach the outlet can be lengthy, and in many larger homes this delay can last as long as three minutes. Relocating your tankless water heater to a more central location is the only way to cut down on lag time.

Expert Insight

You will always want to check the minimum flow rate of any tankless water heater before deciding which product to purchase. A water heater with a high minimum flow rate can cause several problems, such as having to turn your faucet on as high as it will go to reach the required rate to fire the heater. M. Scott Gregg, a licensed plumber and author of "Profitable Plumbing," recommends to never purchase a unit with a minimum flow rate greater than .75 gallons per minute (GPM) for residential applications. He also recommends choosing a unit with a minimum .5 GPM capability. Debris inside your faucet aerators and shower heads can also cut into your flow rate, so your fixtures may need to be cleared out regularly.

References

• Tankless Water Heaters 101
• Tankless Water Heaters