Sunday, January 23, 2022

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Home Improvement Tips

Greetings everyone and Happy New Year! I would just like to start with a humble “Thank you!” for your continued following. I wish you all the best life can offer in the new year to come. I know for many, including myself, this past year was full of challenges and big changes. I am hoping these things only make us stronger. 

Tankless hot water heaters

This week I will cover information on tankless hot water heaters. I have gotten quite a few questions about them this past year: Who are they best suited for? Are they one size fits all?

Sizing and desired use are the most important criteria for choosing a unit. Do you want the unit to supply hot water to your whole house or only one sink or shower?

Know that if you buy one that is too small, your water will be cold or just warm. If you buy a unit that is too big, you will waste energy and there will be no long-term savings.

Sizing: Determine gallons per minute and desired temperature rise

Gallons per minute

Do this test to determine the appropriate size unit for the whole house:

Turn on every faucet one at a time. Run the hot water for one minute, then the cold. Using a gallon bucket, measure how much water comes out of the hot side in one minute. Do the same for the cold. Repeat the process for each shower and tub. Add up the total amount of water. This will give you the maximum gallons per minute (GPM) at peak use.

Temperature rise

Next, do this test to determine the desired temperature rise between the cold water coming into the house and the hot water coming out of the tap.

Using a battery powered kitchen thermometer (like the one you use to test meat for doneness), test the temperature of the cold water at the faucet closest to your water heater. It should be between 50°-57°F depending on where you are in the country.

Decide the how hot you want your hot water to be. For safety reasons, the temperature should be set between 110°-120°F. For reference, keep in mind a hot tub is between 100°-110°F. Also, if you have small children or elderly family members, the lower end of the range will be safer for them. Subtract the cold water temperature from the hot water temperature. The result is your desired temperature rise.

Note: Cold water temperatures vary from warmer climates to colder ones. In Florida, cold water may be as warm as 70°F. In the Dakotas it could be as cold as 33°F in the winter.

Heating Source

Next, determine your current hot water heating source. It will be electric or propane in the Dakotas; electric, propane or natural gas in other areas.

It is recommended to keep the same fuel source when you switch to a tankless system in order to save money. For new construction you may want to explore all the options. In many cases a gas source may be cheaper in the long run.


Now that you have all the needed information, you are ready to pick the right unit for whole-home use.

Gallons per minute

Remember, GPM is your maximum possible usage. It’s based on an unreal situation (all the taps running at once) and is meant to be used a guide.

For a more realistic scenario, I suggest you calculate the GPM for two showers, two sink faucets, and a running washing machine as a normal situation. This would be calculated as below:

2.5 GPM x 2 showers = 5 GPM

0.5 GPM x 2 sinks = 1.0 GPM

1.5 GPM x 1 washing machine = 1.5 GPM

Total GPM = 7.5

Round up. The tankless unit will need to be 8 GPMs. Most home units are 6 or 9 GPM. 

Temperature Rise

Let’s say your cold water is 35°F in January and your desired temperature is 110°F. This gives you a desired rise of 75°F. You will want a unit with a desired rise of at least 75°F but probably not more than 80°F. With this information you can go to a retailer such as The Home Depot and get the right size or contact a local plumber.

Units for one or two faucets

Follow the same rules as above for sizing.

These units are smaller and are meant for use in one room, say a bathroom with one or two faucets. They normally go under a sink or in a nearby closet. They come in 110 or 240 volts. Keep in mind you will probably need a dedicated electrical circuit.

In my opinion these are great for workshops, seasonal small cabins, or employee bathrooms, but not ideal for home use due to the added cost of running the electrical to the location.

Additional Costs

• Framing (These units are heavy.) • Electrician

• Venting • Plumber

• Roof add-ons or siding repairs due to venting (I do not recommend roof venting.)

• Emergency drain in case of failure

Also understand that like, just like a tank hot water heater, these units do wear out. So plan ahead for your next replacement.

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