Code Requirements for Water Lines Both the IPC and IRC state that all water lines as well as sewer lines must be a minimum of 12 inches below grade, i.e., a foot underneath ground level.
Your water line must be buried at least 12 inches below the frost line to meet local code requirements. However, a minimum depth of 6 inches below the frost line is often recommended for extra security against freezing.
When you are digging the trench for your new waterline, be sure the waterline is 12-inches below the local frost depth, but in no case less than 2 feet underground.
California Plumbing Code 2007 Edition (news to me): Section 609.1 states: Minimum cover shall be 12" below finish grade or minimum 12" below the local frost depth. So, 18" below finish grade will be fine and I know on occasion, you get frost in Danville (rarely).
It is recommended to use a 'blank cap end' (made from plastic or rubber) with a purpose-made hole with a grommet to allow the water pipe to pass through. The water pipe should be laid at depth of 750mm (minimum) to 1350mm (maximum). Trenches should be lined and backfilled with sand or soft earth, not rubble.
Generally, this clause requires a minimum depth of 300 millimetres unless the water service is subjected to vehicle loading which would requires a greater depth of between 450 millimetres and 750 millimetres dependant on the above ground surface. other services including gas or electrical and drainage pipes.
Underground pipes are heated by the earth, so they don't usually freeze, but it can happen. The depth of the pipes and the piping material help prevent freezing. When temperatures are around 20 degrees or lower for long periods of time freezing may be an issue.
This means that you would typically want your water lines to be at least 4.5 feet below the ground level or possibly even deeper if you live in the mountains or the foothills. The sewer lateral leading from your house out to the municipal sewer main should also be at the same depth as it could also freeze.
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).
It's not just a pipe dream, because you can still do it on your own! Running water lines in your house comes down to knowing what tools you'll need, and how to use them to repair or install brand new 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.
Cost per Foot
Installing a water main costs an average of $50 to $150 per linear foot. Prices may reach as high as $250 per linear foot in areas with high cost of living and for lines that are difficult to access.
High-density polyethylene (HDPE) pipe is a good choice for underground water lines because of how the pipe is connected. Rather than using joints, which can leak, or glues and cement, which can degrade over time, HDPE pipe is connected via plastic fusion.
The minimum cover required when the drainage system is in a traffic area with drainage pipe diameters from 100 mm through 1200 mm (4”-48”) must have at least 0.3 m (12”) of cover over the pipe crown, while 1500 mm (60”) pipes must have at least 0.6 m (24”) of cover.
Running a PEX line underground is beneficial because of the pipe's flexibility, temperature resistance, and lack of a need for multiple connections along its length. In areas with aggressive soil or water conditions, plastic or brass PEX fittings are recommended.
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.
International Plumbing Code states exterior water supply system piping should ideally lie 6 inches below the frost line and not less than 12 inches under grade for best performance.
Dig-up test results in the U.S. and around the world indicate that PVC pipe can be expected to provide reliable service in excess of 100 years.
Flexible piping systems such as ABS or PVC have less structural strength than rigid metallic piping systems, which is an important consideration when designing systems buried in unstable soil.
Avoid freezing pipes
According to 'The Department of the Environment', they recommend that pipes should be buried at least 600mm (two feet) underground. At this depth, the soil acts as a natural insulator and prevents them freezing.
Water and sewer lines are typically 3 to 4 feet deep depending on the climate, but they can be deeper. Some sewers are buried between 20 and 30 feet below the surface. You may think that the max depth utilities will be found is around 30 feet, but there are cases where they will go deeper.
Eighteen to 24 inches is fine in most cases.
It depends. While pipes themselves don't freeze, the water inside of them does when the area around the plumbing reaches the freezing point. Even if the temperature outside is 32 degrees, pipes underground, for instance, may not be unless it's lower than 32 outside.