Water Hardness Removing Chemical

I would like to know how it is possible to reduce water hardness to zero. I got a sample from a supplier, prepared the 50% solution and added 5 ml of it to reverse osmosis (RO) with salt rejection = 1. Initial water hardness was 700 ppm and after adding the chemical it dropped to 0 ppm. Moreover, there was no sludge forming. How is this possible? Has anyone ever used such an efficient chemical?  What were the best results you have ever managed to achieve?