jimbo, IIRC, the only softeners/filters that use 3/8" drain line are older Sears and Rainsoft. All others use a minimum of 1/2" CTS (not to include CPVC) and they will in some instances due to the length, require 3/4". That depends on the make of the control valve and a few other things like elevation from the control valve etc..
Vinyl tubing should never be used because it kinks very easily and has a reduced ID and kinks cause failure of the equipment. Continuous run PE is the best material and is usually suggested by all control valve manufacturers; such as Autotrol/GE, Clack, Erie, Fleck etc.. The big box stores have been going to it for their GE, Whirlpool, North Star, Morton Salt and Sears/Kenmore brands.
I can't believe ID requires a separate hard water faucet at the kitchen sink! I sell softeners all over the US (delivered one to ID yesterday) and haven't heard of that anywhere including WI, MN, AZ etc. where there are many folks mistakenly thinking it's a good idea. I have many people cuss their hard water at the kitchen sink plumbing.... It's a really dumb idea, especially if there is iron, manganese, H2S etc. in the water!
For those concerned about the added sodium in their softened water. To calculate the added sodium from a softener, multiply the gpg (grains per gallon) of hardness by 7.85 (mg/l). I.E. 20 gpg hard water * 7.85 = 157 mg added sodium per liter (that's roughly a quart). Check a loaf of white bread and you'll see the sodium content varies from 120-150 mg per slice. An 8 oz glass of skim milk usually has 530 mg of sodium. And for those on sodium restricted or low sodium diets, those folks know how to adjust their intake of sodium and can plan accordingly IF they drink any of their daily required 8 8 oz glasses of water per day. And who does?
Also, all water has some naturally occurring sodium in it, so those wanting less sodium in their diet should test their non-softened water for sodium. Or simply eat a few less pickles or potato chips or pretzels, or less ham etc...
Check this out:
http://www.awqinc.com/sodium_softening.html
Here's a picture of that ID softener and his loop.
Gary
Quality Water Associates