I've recently had a water softener put in, and I'm looking to
configure it for the most efficient salt usage with an appropriate
regeneration time.

The softener itself is the equivalent of a white-box computer. It was
sold as a unit (by CAI Technologies), but I could have achieved the
same result just by ordering parts separately, if I were more
comfortable with my knowledge of the technology involved.

The control head is an Autotrol 762/255. The resin tank contains 1.5
ft^3 of Sybron Ionac C-249 cation resin.

I am using KCl instead of NaCl, for a few reasons.

My water hardness was measured by the softener retailer as 16gpg from
a sample I sent. The latest quality report from my water company
shows hardness as ranging from 105 to 339 ppm (~6-20gpg). I find it a
bit strange that it varies so much, since the water comes from a
single well that's right at the corner of my property. For now, I'm
assuming that it stays at the high end, but will be doing some
periodic testing to make sure.

Right now, I have the control head set at 16gpg, with the factory
default of 9lb/ft^3 of salt and subsequently calculated 43K grains of
softening capacity (using its built-in salt table which says 9lb/ft^3
has a capacity of 28673 grains/ft^3).

I've downloaded the data sheet for Ionac C-249, and they have a
capacity chart which seems to show 25000 grains/ft^3 at 9lb/ft^3 of
salt with 20gpg water. The line seems to cross 20000 grains/ft^3 at
6lb/ft^3 of salt.

Assuming 200 gallons of usage per day (which is a bit more than what
we average), I calculate these results:

6lb/ft^3 salt, 30K grains = 9 days between regeneration (41/year), 9
lb KCl per regeneration (369 lb/year)

9lb/ft^3 salt, 37.5K grains = 11 days between regeneration (34/year),
13.5 lb KCl per regeneration (459 lb/year)

That's more than two 40lb bags of KCl (at $9.47 each), versus around
400 gallons more water used in a year (at about $0.01/gallon).

Can anyone with a bit of experience with water softeners give me a
sanity check on those numbers? Is there a better source for grain
capacity on this resin than a low-resolution chart?

For that matter, is there any difference in resin capacity between Na
and K ions?
--
- Mike

Ignore the Python in me to send e-mail.