A frost free sillcock is designed to protect the outdoor plumbing of your home. A frost free sillcock puts the faucet’s flow valve well within the warm, cozy, or heated walls of your building. This means that if there is a sudden change in temperature which results to a sudden freeze, and you forgot to turn off and drain the water spigot for the winter, the frost-free sillcock can help by dramatically reducing the chances of you having a burst pipe.
An anti-siphon, on the other hand, also known as the vacuum breaker in a water spigot is now required by all plumbing organizations and building codes. This feature is built into the new types of frost-free sillcock, and it can also be added to existing ones.
This feature prevents unsanitary water to be pulled back through an outdoor hose at the same time, preventing your water system from being contaminated.