Reader Sandra Quick (Grand Rapids, MI) wrote us
with this question. "I have old regulators, BCs, wetsuits,
fins, etc. Is there any place that would accept this stuff?
Most places don't want the liability, but I can't imagine
some of it can't be salvaged. Help! I need some space, as
I hope Santa is bringing me new gear."
Unfortunately, there isn't a simple way to recycle
  dive gear. The best bet is to first contact the manufacturer
  -- many are putting together recycling programs for
  their gear. While some companies will take their obsolete
  products back for free, others require you to upgrade to
  a newer product before they'll recycle. The gear easiest
  for them to recycle are BCDs, regulators, dive computers
  and instruments. Of course, whether companies use
  what you give them or just trash it is another question.
Second, ask your dive shop. Many have trade-in
  and resale programs for some dive gear. But those most
  likely to be tossed are rubber products -- masks, fins and
  wetsuits -- because there's often no place that recycles
  that material in small quantities.
Tanks are easier to recycle and therefore more likely
to be taken back by dive shops. Aluminum tanks made
after 1990 can often be re-certified and put back into use.
If they're beyond repair, Jack Kuhn of Harbor Diving
Center in Sausalito, CA, says he can still take them. "I
have a few guys who like to cut them up and make bells
and gongs out of them." Aspiring artists can get good
ideas, from lamps to BBQ grills, in Fred Garth's article
"Tubular Reincarnation: Uses for a Dead Scuba Tank,"
in the January 2012 issue of Australian magazine Scuba
Sport (it's available to read for free at ScubaBoard; just
type "tubular reincarnation" in the search box).
If your gear still has some life in it, consider re-selling
  it online at eBay. Donate it to your local Salvation Army
  or Goodwill Store, where profits go to job-training
  efforts and career services. (Some don't accept dive gear,
  so ask beforehand.) Or donate your gear to a nonprofit
  organization that uses divers, like your local aquarium.
Finally, local recycling centers remove useful metals
  from electronics and other products - that might be the
  most certain way to ensure what's useable doesn't just
  get trashed. Check the website www.gotscrap.com for the
  scrap metal recycler nearest you.