Re: Sillcock absent Shut-off Valve
Since you describe a sillcock with an anti-siphon, you most likely have a "frost-proof" sillcock. With this style, the actual valve (where the washer meets the seat) is anywhere from 6 to 18 inches inside the wall/floor. There's a long rod (stem) that runs from the handle inside the faucet body to the washer. The principle is that the valve is in the heated envelope of the house and protected from freezing.
Originally Posted by Top Cat
You also describe that the piping is up against the subfloor and that there is a significant amount of insulation below it and there is heated area above. I think it's highly unlikely that the piping and sillcock will freeze, providing you remove the hose in freezing weather to allow the sillcock to drain. Covering the sillcock should only be necessary during prolonged periods of freezing weather below 20 degrees Fahrenheit.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.