I figured period 12 would be doable, but it's a massive pain.  Period 16 is far easier as you can use a lot of period 4 atom handling.  No anime, dupe + triplex + calcify is good enough to handle salt vs water and it doesn't require throwing anything away or pulling atoms from new sources.  It seems that the only way to build the output is three separate bonding stations.  I was able to reuse one of them for the final join, but the tinkering I did from my first design saved about 50wsum by adding another bonder for joining the water to the rest, meaning 4 bonders, 2 triplex, 3 debonders, a duplicator and a calcifier.

Arm 13 bothers me deeply, and for the all-water test case it takes up extra area and 3 more cycles.  I don't think that 20 wsum will burn me but who even knows.  I got tired of staring at it with no way to fix it.