Bring water and quinoa to a boil in a saucepan. Reduce heat to medium-low, cover, and simmer until quinoa is tender and water has been absorbed, 15 to 20 minutes. Remove from heat, uncover and allow to cool, about 30 minutes.
Toss quinoa, spinach, hard-boiled eggs, walnuts, and sunflower seeds in a large bowl until combined. Top with ranch dressing.