Tankless Water Heater Gallons Per Minute

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Many households, especially, in places with very cold weather, rely heavily on their water heating systems for the continuous supply of hot water. The continuous supply of hot water, however, is very vital to the well-being and proper functioning of any household. As such, any failure of the water heating systems may spell disaster to the occupants of a household.

Types of Water Heating Systems and Advantages of Tankless Heaters

Any appliance that supplies continuous amount of hot water is called a water heating system. Water heating systems have different types. First, there is the storage-type water heater (tank-type) that was previously the most popular type of water heating systems for household and commercial usage.

There is also the tankless water heater. This water heating type is also called “continuous flow” water heater because it provides a continual supply of hot water using a heat exchanger coil inside its unit. The water that flows through the unit comes in contact with the heat exchanger coil heating it up. The tankless water heater is gaining wide popularity nowadays for the following reasons:

  • It provides a continuous supply of hot water as compared to the tank-type water heater.
  • It can be installed around the household as “point-of-use” water heaters.
  • It also allows you to save on your energy consumption in the long run.

Tankless water heaters come in various sizes. Hence, even though each unit is designed for providing a continuous supply of hot water, you still need to figure out the right size for your household needs of hot water. It is important that you know how much hot water your household would need before buying a particular model or brand of tankless heater.

How Do You Figure Out the Right Size of Tankless Water Heater?

You need to know several valuable factors so that you can buy the right size and model of tankless water heater. These factors include the following:

  1. First, you need to know the total number of devices that you would like to supply with hot water and the total flow rate of all these devices. You can get the total flow rate of all these devices by adding up the flow rate of each individual appliance that you would use at the same time. The outcome flow rate will be the desired flow rate that your water heater must be capable of.

You may be a bit confused at this point but let me clarify it by an example. If you run two hot water faucets that have a flow rate of 1 gallon per minute each and you also use a shower head that has a flow rate of 3 gallons per minute, you simply need to add their flow rates. Two hot water faucets of 1gpm each is equal to 2gpm plus 3gpm of the shower head equals to 5gpm (total flow rate). So, the best tankless water heater that you should avail of must have at least a flow rate per minute of 5gpm.

  1. You also need to determine the necessary temperature rise afforded by a tankless heater. You can figure out the temperature rise by simply subtracting from the desired output temperature the incoming water temperature. If the incoming water temperature, for example, is 55°F, and you want to heat the water up to 105 to 115 degrees Fahrenheit, you simply need to subtract 55°F from 105°F. The result would be 50°F. So, 50°F would be the required temperature rise that your prospective water heater must be capable of providing.

Understanding Gallons Per Minute and the Desired Maximum Flow of Hot Water

Gallons per minute is the unit of measurement that indicates the flow rate of liquids through a pipe. On average, each person in the U.S. uses 100 gallons of water per day. If there are six persons in a household, then the total consumptions per day would be approximately equal to the 600 gallons per day.

The ideal tankless water heater should supply around 20% of the total water usage per day of a household. Thus, if the total household usage for six persons is 600 gallons per day, the water heater should provide at least 20% of 600 gallons per day which is equivalent to 120 gallons of hot water per day or around 4 gallons per minute of hot water. However, a family of six should ideally go for a tankless water heater that could provide 5 to 7 gallons of hot water per minute.

You should not undersize your water heater. You surely need to know the desired maximum flow rate of hot water that your household really needs.

Many households only have one major hot water demand at a time, typically, a demand for hot water from two shower heads. Thus, a tankless water heater capable of providing 3gpm of hot water at a time would suffice for these needs. Lastly, you should consider the changing temperature of the incoming water. The temperature of the incoming water may change from day to day. Thus, you should make provision for these changes.



Welcome to the Night Helper Blog. The Night Helper Blog was created in 2008. Since then we have been blessed to partner with many well-known Brands like Best Buy, Fisher Price, Toys "R" US., Hasbro, Disney, Teleflora, ClearCorrect, Radio Shack, VTech, KIA Motor, MAZDA and many other great brands. We have three awesome children, plus four adorable very active grandkids. From time to time they too are contributors to the Night Helper Blog. We enjoy reading, listening to music, entertaining, travel, movies, and of course blogging.

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