I'm replacing an old conventional bib and went to get new frost free type but not sure why I need it. The one that I'm replacing never caused any problems but is there a code issue with replacing with the newer anti-siphon type? They have nice 1/4 turn ball valve for like $6 or frost free for $22. I don't use it in the winter time and just shut off valve inside house and leave bib open. Am I missing something? TIA for input. I'm a carpenter/handyman for 20 years.
The concept of the frost-free is that since the guts are located inside the house (and hopefully heated!), there's no water in the outer portion of the valve to freeze, so if you occasionally use the outside faucet or forget to turn it off for an early cold spell, you won't end up with a burst pipe. Keep in mind that (with one exception), if you leave the hose on it, the water can't drain, and it will still happen.
Most places require an anti-siphon (backflow preventer) to be part of an outside faucet. This is to prevent sucking in contaminants if there's a hiccup in the supply system while the open hose is sitting in say a bucket or a puddle. There are inexpensive add-on versions if the valve you buy doesn't have one built-in.
So, depends on what you want.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013