What Size Tankless Water Heater Do I Need for My Family in Marshfield, MO? Calculate GPM, Temperature & More

Tankless water heaters are becoming more and more popular in businesses and in the home. They bring instant hot water without the need to keep water hot in a tank. Tankless hot water removes the upkeep of a hot water tank and the frequent cost of repairing and replacing. When you decide to convert or install a tankless hot water heater in your home, you will need to determine what size unit you will need. Randall’s Plumbing will help you determine what size tankless water heater you will need to ensure you get the right size.

Flow Rate; How Do You Calculate GPM for a Water Heater?

To determine what size tankless water heater you will need, you will need to know how much hot water flow you will need or use. Each tankless water heater produces only so much hot water at a time. They are measured in gallons per minute (GPM). You will need to determine how much hot water you use. In order to determine the right size, you will need to add all the plumbing fixtures in the home. Here is an average flow of hot water to the different types of fixtures or appliances:
Bathroom Sinks – 1.0 GPM
Kitchen Sink – 1.5 GPM
Bathtub – 4.0 GPM
Shower Head 2.5 GPM
Dishwasher – 1.5 GPM
Washing Machine – 2.0 GPM
With a tankless water heater you cannot use two major appliances or water fixtures at once. So you do not add up all of the plumbing fixtures and appliances as if everything is running at the same time. However, calculate your GPM with two to three sinks running at the same time or an appliance is running while you use a dish sink. You will need to look at your daily water usage and seek what combination of appliances and fixtures are often used at the same time and figure out what GMP you will need. Where every household hot water needs vary there is no one answer for each home. Unfortunately you must do the math.

What is the Ideal Temperature for Your Domestic Hot Water?

Next to knowing your flow rate, you next must consider the temperature of hot of water you will need. This is known as temperature rise. To calculate your hot water temperature it is not as easy as to say “I like my shower at 120 degrees. Even so, that is the average hot water temperature setting for most tanks and tankless water heaters. A tankless system must know how much heat to give the water to produce the desired temperature. Each state and region ground water varies in temperature. The ground water temperature must be measured to know how much to rise the water that is passing through the tankless water heater. For example, if the ground water is around 52 degrees, the water heater must heat another 68 degrees to produce the 120.

Residential & Commercial Plumbing Repair, Replacement & More in Marshfield, Conway & Greater Lebanon, Missouri

Once your flow and temperature rise has been determined, put the two together to see what size tankless water heater you will need for your home. As it can be confusing to figure yourself, you may want to simply seek out a plumbing service that can help calculate what size tankless water heater you will need. If you install instant-hots on sinks and other fixtures, this will change the tankless water heater size as well. If you want a tankless water heater installed and need help sizing and installation, contact Randall’s Plumbing today.

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