On or about Thu, 10 May 2007 15:09:52 -0700 did "SJF"
dribble thusly:


On the KCl vs. NaCl thing --

I took the number from an unremembered source I considered probably
reliable. Checking, I find that the molecular weight of KCl is 27% greater
than that of NaCl so you would need the extra weight of salt to provide an
equivalent recharge. Since the solubility of KCl at 20 degrees Centigrade
is essentially the same as for NaCl, the water used for brining would need
to be increased 27% to get the extra salt.

This is how I should have approached the question. It's been a while
since my last chemistry class, where that mode of thinking would have
been natural.

Now, if only I knew what temperature the softener assumed for
calculating the quantity of water to push back into the brine tank.

I'll probably be safe going with 8lb/ft^3 instead of 6lb (at the same
30K grain capacity), which more than compensates for the molecular
weight difference, and thus leaves a bit of a buffer for the
temperature being lower than the softener may expect.
--
- Mike

Ignore the Python in me to send e-mail.