Here is a real easy way to make sumac tea.
Like green tea sumac berries are a natural source of tannins. In addition, sumac berries contain gallic acid, an antioxidant, which may prevent cancerous cell production. Gallic acid it also used in psoriasis treatments, external hemorrhoids and as an astringent.
The tartness of sumac is partly due to ascorbic acid (vitamin C) so one also has a health incentive to drink this tasty, natural beverage.