Your water line must be buried at least 12 inches below the
The IPC and IRC also state that all water and sewer lines must be at least 6 inches below the typical frost level for the area to help ensure that the pipe can't freeze.
Even buried, underground water pipes can be subject to freezing.
In most parts of the country, as long as your pond is deeper than 6 inches, it is very unlikely that it will completely freeze.
The line varies by latitude, it is deeper closer to the poles. The maximum frost depth observed in the contiguous United States ranges from 0 to 8 feet (2.4 m). Below that depth, the temperature varies, but is always above 0 °C (32 °F).
So it is paramount that you remember that 600mm is how deep you should aim to have your water pipes buried if you are going to prevent water from freezing inside of the pipes.
The top of the pipe should be buried not less than 1 foot (0.3 m) below the frost line. In those locations where frost is not a factor, the depth of cover should be not less than 2- 1/2 feet (0.8 m) to prevent mechanical damage. Pipe should be buried below the frost line when entering streams and other bodies of water.
You may wonder how deep the frost line is. It can vary wildly. In the coldest climates in the USA, the frost depth can be deeper than eight feet. In warmer parts of the country, the frost depth may be less than one foot.
When ground temperatures drop to 0°C (32°F), the water trapped in sediment, soil, and pores of rocks turns to ice.
The Lifespan of a Water Line
The mainline provides homes, particularly within a suburban or urban housing development, with running water. Typically, main water line pipes last decades. Some experts estimate that they last around 70 years, though this can vary from development to development.
Water tanks can freeze during winter. They also get very hot during the summer. Above-ground tanks are often smaller than underground tanks.
Your pipes are at risk of freezing any time temperatures drop below 32°F. However, it's much more common for pipes to freeze when temperatures dip below 20°F. The longer the weather remains below freezing, the more likely it is your pipes can freeze if not properly protected and winterized.
Frost depth (or the “frost line”) is the depth in the soil above which water may freeze during the winter. Colder areas with longer winters have deeper frost depths, and areas with milder winters have shallow or no frost depth. Water expands when it freezes.
My recommendation is to bury sprinkler lines 8-12 inches. I usually try to keep a standard depth of 10" because it provides more safety if I need to do some type of ground work so I don't have to worry about hitting lines.
When posts, foundations, footings, and other supports are installed above the frost line, the structures become vulnerable to shifting, cracking, and other damage that may occur when water below the foundation freezes and expands.
The International Plumbing Code states that “Exterior water supply system piping shall be installed not less than 6 inches (152 mm) below the frost line and not less than 12 inches (305 mm) below grade.” Above the frost line, the ground can heave up, shifting whatever is in it or freezing the pipes' contents.
In summary, underground PVC pipes are indeed likely to freeze in cold environments, especially when buried too shallowly, the soil is moist, or the outside temperature is too low.
PEX is flexible and performs better in freezing conditions than rigid pipes like copper, PVC and CPVC. These other pipes are more at risk of the water freezing in them, making them susceptible to weakening and bursting. Explore how PEX performs in cold weather and how to prevent future pipe bursts.
The water service lines can freeze when the ground frost gets deep enough to encase your service line in ice. However, this generally happens only when your service line is less than 40" below the surface of the ground, or your service line passes through a stream that washes out your service line.
The burial depth for water lines depends on local frost levels and plumbing codes. As a general rule, water lines must be buried below the frost line, the depth where the ground freezes in winter. In Northern Colorado, this depth can range from 36 to 48 inches, depending on your location.
Pipe for conveying liquids susceptible to freezing should be buried no less than 12" below the maximum frost level. Permanent lines subject to heavy traffic should have a minimum cover of 24". For light traffic, 12" to 18" is normally sufficient for small diameter pipe (typically < 3" diameter).
Eighteen to 24 inches is fine in most cases.