burkkof wrote:After two days of using the new filter, I noticed that the flow is faster than before, what should be the effect of the softness of the water on the extraction behavior?

It's fairly well accepted that an increase in bicarbonate alkalinity will reduce the flow rate, but with your softener the alkalinity is the same before and after.

Some early research has indicated an increase in brewing time (slower flow) as total hardness decreases. The Illy book advises that softening below 2 French degrees (20 ppm as CaCO3) may require a coarser grind to compensate for an increase in percolation time. But later research (L. Navarini, D. Rivetti 2010) has not found that to be the case. The Craft and Science of Coffee book simply says: "At high hardness and equally high (or lower) alkalinity, no increase in percolation time was observed. "

Irrespective, I think your strategy is to tighten up the grind, brew, and taste. For any new coffee you can tighten the grind and try it at a slow ristrettoish ratio and flow rate, then loosen the grind and try it at a faster flow and longer ratio, and adjust between there based just on taste.

Thanks Pat ! Really appreciate it for sharing such an important info and valuable advices.

Ricki