The pool store guy also told me that apparently the city has by-laws that say you can't backwash salt into the sewers, which seems rediculous to me, as the city use salt during the winter for the roads. Does he have a point though that the salt will corrode my heater? I have a crappy Jandy LXi 400N.
Switched my pool to salt this year.
I really, really like the couple who own the pool store near me, especially the wife, but that didn't mean they, or any other pool store employees automatically know more about pool care than me. After dealing with a green pool last year due to massively high CYA that had built up over the years from previous owners, I stopped listening their advice (unfortunately, not before spending $$ or "clarifiers" and algicides at other pool stores when I grew desparate to fix the problem that loaded my pool up with copper).
When I tested my salt before conversion, I had
1800ppm of salt in my not-saltwater pool. That's more than halfway. I then did a partial drain and refill to get rid of all that copper and CYA, so than I had to add more...but still, the amount of salt in your pool already may surprise you.
There are definitely rules in various places about where and how you can backwash. Around here, you definitely aren't supposed to backwash into the sewer, you're supposed to do it into the rainwater runoff. Some places don't let you backwash at all without treating. I got very tired of backwashing my DE filter -- though in retrospect it was because I had an algae problem due to high CYA that I just didn't know about thanks to my DE filter... At any rate, this year I got a new cartridge filter. No more backwashing anyway.