The first time I made it I erroneously assumed since it is tart like lemonade it would require as much sugar. I learned, fairly quickly, that it does not. So easy on the sugar and add it a little at a time, making sure all is dissolve before adding more. Then just chill and serve.
1/2 c. sumac powder
1/4 c. sugar (to taste)
6 c. warm water
Combine the water and the sumac powder, stir, and let it sit for at least 2 hours.
Take a paper towel and separate the layers. Line fine mesh strainer with the single layer of paper towel and collect the liquid in a bowl. Remove the paper towel and line the strainer again with a non-separated paper towel and strain again.
Add the sugar to the liquid to taste and chill.