Frost free hose bibs are a requirement if you live in a climate with cold temperatures in the winter and want (or need) an outside water spigot. During winter if there is water remaining in the hose bib, winter temperatures can reach well below zero in many locations, the water will freeze. Because water expands when it freezes, this can cause serious problems, specifically, a cracked or split pipe that will begin leaking the next time that you turn on the outside spigot.
Even frost free hose bibs freeze from time to time. However, there are certain precautions that you can take to make sure that your hose bib has a long life.
The number one, most important thing that you can do to prevent your hose bib from splitting is to remove your hose from the spigot before temperatures drop below freezing. The reason why this is important is simple, with the hose attached; the frost free hose bib cannot drain the water as it is intended. The water remaining in the hose will eventually freeze and expand. If the water freezes in the spigot or pipe, it will most likely cause the spigot to fail.
Another common mistake that people make is leaving attachments such as splitters or quick releases on the end of the spigot. These also do not allow the water to drain from the spigot and will cause problems. Finally, if the spigot has a slow drip, the drip will freeze around the spigot and ice will continue to build up. This can be the most damaging in terms of eventual repair.
If your frost free hose bib has frozen or if your basement has filled with water when you turned on the outside spigot for the first time, call a licensed plumber immediately. He or she will be able to fix the problem and advise you on how to avoid this kind of repair in the future.