Is this an emergency?

[JKalchik]

My frostless/anti syphon was leaking one morning ( quite a steady stream) I was able to shut it off from the inside.
I talked to a plumber at work and he recommended the cap. His reasoning was to stop the cold air from entering 12" back to the inside washer.
Like I said when installed right, any leftover water drains out of the body. Capping it and putting a insulated boot on protects the tube from cold air infiltration.

That just does not make any sense to me. The valve/washer SHOULD be in a conditioned space, that's the point of a long body that drains. If the valve begins leaking, it's going to either fill the body until the air pressure reaches equilibrium with a cap in place, or without a cap, it should just drain out. Once you have still water in the body, you now have a freeze hazard. With a good valve, capping after the body drains shouldn't be an issue. I didn't see the replacement here a couple of years ago, I'd suspect an 8" body length but I don't see the valve assembly from under the sink.

 

[Joe Anshien]

I think this spigot had a slight leak. I'm not sure when this weather is supposed to get above freezing. I looked in my crawlspace and I don't see any water in there. There's no internal cut off valve. This weather is crazy for this area. That hose is not connected. I tried to thaw that ice with a hair dryer. I think I'd be there all day. That hose was not connected. I've got these vents around the house I'm trying to cover with duct tape. It looks like they at one point had covers. There's a screw in the middle where a wing nut could be fastened, but the vents are a weird old size.

The vent covers are pressure fit. Just bend them a little and smush them in there. All of mine have been replaced with temperature sensing vents that automatically close when it gets cold.

 

[JKalchik]

That just does not make any sense to me. The valve/washer SHOULD be in a conditioned space, that's the point of a long body that drains. If the valve begins leaking, it's going to either fill the body until the air pressure reaches equilibrium with a cap in place, or without a cap, it should just drain out. Once you have still water in the body, you now have a freeze hazard. With a good valve, capping after the body drains shouldn't be an issue. I didn't see the replacement here a couple of years ago, I'd suspect an 8" body length but I don't see the valve assembly from under the sink.

FWIW, I shot the stem under the sink (with an IR thermometer) that leads to the outside hose bib this morning at 0600, with an outside ambient temp of around -18 F. I got a temp of 39 degrees, but this is also at last an inch or more on the pressure/inside side of the valve.