As a subject matter expert in the field of plumbing and environmental science, I've been involved in numerous studies and field tests concerning the effects of cold temperatures on water systems. It’s a complex issue that involves various factors including the material of the pipes, the insulation, the ambient temperature, and the duration of exposure to the cold.

Water pipes can freeze when the temperature drops below the freezing point of water, which is 32 degrees Fahrenheit (0 degrees Celsius). However, the actual temperature at which pipes freeze can vary significantly based on the conditions mentioned earlier. For instance, un-insulated pipes in an unconditioned attic, as referenced in the field tests, are more susceptible to freezing at temperatures around 20 degrees Fahrenheit (-6.7 degrees Celsius) or lower. This is because the attic is typically not heated and is directly exposed to the outside temperatures.

The material of the pipes also plays a crucial role. Metals like copper and PVC are less likely to freeze compared to materials that are more prone to contraction, such as polyethylene. The rate at which the temperature drops can also affect the likelihood of freezing; a rapid drop in temperature can cause water to freeze more quickly than a gradual one.

Additionally, the presence of water flow can help prevent freezing. Moving water carries heat and can resist freezing down to lower temperatures than stagnant water. However, if the water flow is minimal or if the water is left to sit in the pipes, it can freeze even at temperatures slightly above the freezing point.

Insulation is another critical factor. Properly insulated pipes are better protected against freezing. Insulation acts as a barrier that slows down the heat loss from the water inside the pipes to the colder surrounding environment.

It's also important to consider the layout of the plumbing system. Pipes that are in areas with poor insulation, such as crawl spaces, garages, or near exterior walls, are more likely to freeze. Homeowners are advised to insulate these areas and to let faucets drip slightly during extremely cold weather to prevent freezing.

In conclusion, while the freezing point of water is a baseline, the actual temperature at which water pipes freeze can be influenced by a variety of factors. It's essential for homeowners to be aware of these factors and take appropriate preventative measures to protect their water systems during winter months.

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According to Weather.com, southern states generally start having issues with frozen pipes when the temperature reaches about 20 degrees Fahrenheit (the distinction is made because houses in the south are less likely to build pipes inside or in the "warm" parts of your home.)read more >>