Wash the rhubarb and cut into pieces approx. 1 cm wide. Bring the rhubarb and water to the boil in a saucepan with a lid and simmer for 45 minutes. Then drain through a fine sieve and squeeze out the rhubarb mixture with a wooden spoon.
Bring the rhubarb stock to the boil again with the sugar in a saucepan, then fill into clean glasses / bottles and immediately close tightly.
If you want to be on the safe side, you can boil down the jars with water after closing them in a saucepan or in the oven. So far, it has always worked without it for me and the glasses were tight just from the hot filling.
After cooling, you can store it in a dark and cool place for up to a year. So you have a great concentrate with which you can enjoy refreshing rhubarb iced tea all summer.
To serve the iced tea, you can dilute it up to a ratio of 1/1, depending on your taste, and serve it with lemon, ice cubes and, if you want, mint too.