Average Groundwater Temperatures for the Cities in Rhode Island

Temperature is important to consider when dealing with hard water because calcium dissolves more easily in cold water. Most substances that dissolve in water, such as sugar, do not behave in this manner. Most everyone knows that you can dissolve more sugar in hot water than cold. Calcium has the opposite effect: the hotter the water, the less calcium it can dissolve. If your water source is deep in the earth (higher pressure also contributes to increased calcium solubility) and the groundwater is very cold, you can almost certainly expect hard water. Groundwater is so hard in some areas that water utilities must blend it with surface water to reduce the hardness. If you would like more information on the hard water levels in your area please see our hard water map.

Another important reason to know your average groundwater temperatures is if you are trying to determine which tankless water heater to purchase. The reason for this is because in colder climates the groundwater starting temperature is colder than in warmer climates. This causes the tankless water heater to work harder to increase the water temperature in colder climates, which in turn causes the flow rate to decrease in parallel. For example, if the starting water temperature is 52°F and you need to raise the water temperature to 110°F. Then your tankless water heater must be able to raise the temperature of the water by 58°F while still providing adequate flow to support the fixtures you wish to run at the same time.

How Flow Rates are Affected by Temperature

In the example below, you can see the impact that temperature has on flow rates. This example is based on a tankless water heater that has a flow rate rated for 8 GPM.

Temperature ZoneEfficiency
+71 °F100% (8 GPM)
61 – 70 °F73% (5.8 GPM)
51 – 60 °F58% (4.6 GPM)
41 – 50 °F48% (3.8 GPM)
< 40 °F41% (3.2 GPM)


Flow Rates of Appliances

Based on the corresponding flow rates for each appliance that are listed. A tankless water heater that is rated with a flow rate of 8 GPM (gallons per minute) is capable of running these items at the same time in regions with an average groundwater

temperature of 72°F.

Shower = 3 GPM

Kitchen Sink = 1.5 GPM

Washing Machine = 2.5 GPM

Total = 7 GPM

If you take this same exact tankless water heater and install it in a region that has an average groundwater temperature of 52°F (green zone). This will lower that tankless water heater's max GPM output to 4.64 GPM.

Shower = 3 GPM

Kitchen Sink = 1.5 GPM

Total = 4.5 GPM

As you can see before purchasing a tankless water heater it's important to know the impact temperature has on its ability to heat water and its effect on the total GPM needs of your household.

Rhode Island Groundwater Temperature Yearly Average

CityGroundwater Temperatures


2909 | 2908 | 2907 | 2904 | 2906 | 2905 | 2903 | 2912



2886 | 2889 | 2888



2920 | 2910 | 2921


What Tankless Water Heater Should you Buy if you Live in Rhode Island?

Since Rhode Island's average temperature range is between 51°F and 54°F. It is recommended that you select a green zone Tankless Water Heater. To see the recommended Tankless Water Heaters that apply to the green zone temperatures please follow the link that corresponds to the region of your average groundwater temperature.


Temperature zoneRecommended Tankless Water Heater
< 40 °FTankless Water Heater Recommendations
41 – 50 °FTankless Water Heater Recommendations
51 – 60 °FTankless Water Heater Recommendations
61 – 70 °FTankless Water Heater Recommendations
+71 °FTankless Water Heater Recommendations