Help me solve my water issues!

Not a problem.

xtensive studies have been done. The most common conclusion was as Tom said, not a problem. That being said, I would highly recommend designing the system to be as efficient as it reasonably can be, there is no need to try to break the septic system with massive amounts of unneccesary salt and water. Here is a report from the WQA (ignore the person on this site who says the WQA is a stupid waste of time and money and only suckers would join...) that goes over the septic system and softener debate in fairly good detail. There are other reports out there that back up these reports. http://www.wqa.org/sitelogic.cfm?ID=363

Metered vs. Timered?

Is there a preference? I have offers for setups with metered, and setups with timered. I'm trying to figure out if one has a significant advantage over the other.

Timer is not even legal in many states. Metered always.

Time-clock designs may save you a few dollars up front, but can use significantly more salt and water.

Can a mechanical 2510 be converted to metered? Is it worth it? It's 12 years old, shows some iron discoloration, otherwise working OK, as far as I know.