Simmer the water and the zest in a covered pot for about 12 minutes.

Strain the zest and add water so that it comes to about 2 cups.

Add the sugar and boil over strong heat until you have a thick syrup (when you take a spoonful of the syrup and pour a couple of drops on a small plate, the drops shoud stay round like beads and not spread).

Remove from heat and add the juice after you strain it first, then mix well.

When it cools store in bottles and keep in the fridge.

It keeps in the fridge for quite some time. When you want to drink some, just pour some of the juice concentrate to fill 1/4 of a glass and fill the rest with cool water.