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?