Washington
Average Groundwater Temperatures for the Cities in Washington State
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. It is common knowledge 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 Zone | Efficiency |
|---|---|
| +71 °F | 100% (8 GPM) |
| 61 – 70 °F | 73% (5.8 GPM) |
| 51 – 60 °F | 58% (4.6 GPM) |
| 41 – 50 °F | 48% (3.8 GPM) |
| < 40 °F | 41% (3.2 GPM) |
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.
Washington Groundwater Temperature Yearly Average
| City and Zip Codes | Groundwater Temperature |
|---|---|
|
Seattle Metro Area 98101 | 98102 | 98103 | 98104 | 98105 | 98106 | 98107 | 98108 | 98109 | 98112 | 98115 | 98116 | 98117 | 98118 | 98119 | 98121 | 98122 | 98125 | 98126 | 98133 | 98134 | 98136 | 98144 | 98146 |98148 | 98154 | 98155 | 98158 | 98164 | 98166 | 98168 | 98174 | 98177 | 98178 | 98188 | 98195 | 98198 | 98199 |
52°F |
|
Spokane 99201 | 99202 | 99203 | 99204 | 99205 | 99206 | 99207 | 99208 | 99212 | 99216 | 99217 | 99218 | 99223 | 99224 |
54°F |
|
Tacoma Metro Area 98402 | 98403 | 98404 | 98405 | 98406 | 98407 | 98408 | 98409 | 98416 | 98418 | 98421 | 98422 | 98433 | 98443 | 98444 | 98445 | 98446 | 98447 | 98465 | 98466 |
54°F |
|
Vancouver 98660 | 98661 | 98662 | 98663 | 98664 | 98665 | 98682 | 98683 | 98684 | 98685 | 98686 |
51°F |
|
Bellevue 98004 | 98005 | 98006 | 98007 | 98008 |
52°F |
|
Kent 98030 | 98031 | 98032 | 98042 |
54°F |
|
Everett 98201 | 98203 | 98204 | 98207 | 98208 |
51°F |
|
Renton 98055 | 98056 | 98057 | 98058 | 98059 |
51°F |
|
Federal Way 98003 | 98023 |
52°F |
|
Tri-Cities 99301 | 99336 | 99337 | 99338 | 99352 | 99354 |
52°F |
|
Olympia 98501 | 98502 | 98506 | 98512 | 98513 | 98516 |
55°F |
|
Bellingham 98225 | 98226 | 98229 |
51°F |
|
Mount Vernon 98273 | 98274 |
51°F |
|
Longview 98632 |
52°F |
|
Whidbey Island 98236 | 98277 | 98278 |
53°F |
|
Port Angeles 98362 | 98363 |
53°F |
|
Sequim 98382 |
52°F |
|
Yakima Valley 98901 | 98902 | 98903 | 98908 |
49°F |
|
Walla Walla 99362 |
55°F |
|
Moses Lake 98837 |
51°F |
|
Ellensburg 98926 |
48°F |
|
Wenatchee 98801 |
52°F |
What Tankless Water Heater Should you buy if you Live in Washington State?
Since Washington's average groundwater temperature range is between 48°F and 55°F. It is recommended that you select a green zone or light blue zone Tankless Water Heater. To see the recommended Tankless Water Heaters that apply to the light blue and green zone temperatures please follow the link that corresponds to the region of your average groundwater temperature.
| Temperature zone | Recommended Tankless Water Heater |
|---|---|
| < 40 °F | Tankless Water Heater Recommendations |
| 41 – 50 °F | Tankless Water Heater Recommendations |
| 51 – 60 °F | Tankless Water Heater Recommendations |
| 61 – 70 °F | Tankless Water Heater Recommendations |
| +71 °F | Tankless Water Heater Recommendations |
