Plumbing – What should the water main connect to first: carbon filter or water softener

Okay I will try my best on this one. Living in an arid climate does create quite the change in temperature, do you ever get below freezing there? Code up here is at least 18" underground and sleeved if the water line is not approved for underground. I would suggest PVC sch80 pipe as I believe that is approved. The pressure loss is also minimal for the length of pipe in PVC but the number of elbows you are proposing, which I am counting 9 is a total friction loss of about 38 feet of head which is 16 psi. Now I am not saying you'll loose that much off the piping but the calculation suggest it. That is the garage application. Now on average from a water softener you will also lose about 5 psi. I understand the aesthetics your house is important, but I would keep it outside behind the fence if you guys down there have weather that doesn't go below freezing. If you do I would box it and put heat trace on the softener and lines. I hope this helps.

It sounds like it's an activated carbon filter, which takes organics out of the water (like the sulphur smell), and that it needs to be rebedded (this needs to happen typically once every 3 to 5 years, depending on level of contamination). Once the activated carbon is 'used up', it actually becomes a good breeding ground for bacteria and is worse than completely ineffective. (Aside, this is the same reason that jug-style filters like Britta need to be replaced regularly -- and it's better to use nothing than an old one).

There is not really anything called an "iron filter". Softeners can low levels of iron out, and greensand filters can be used for higher levels, but a greensand filter will have a small tank attached with potassium permanganate (dark purple stuff) in it: