In a medium saucepan, set over medium heat, add the rhubarb pieces, water, sugar and pinch of salt. Simmer for 5 minutes, or until the rhubarb has softened. Using the back of a wooden spoon, crush the rhubarb, being careful because it might splatter! Simmer for an additional minute or so; the mixture should be a pale to bright pink. Pour the syrup through a sieve into a small bowl or glass with a spout.