The fact that the Denver area experiences quite cold winters make it essential that your water line is located far enough underground that it shouldn’t freeze even during an extreme cold snap. That being said, the exact depth that your water line needs to generally depend on local code requirements. If you’ve ever wondered how deep a water line needs to be, here is a full overview of the relevant code requirements and the factors that influence how deep your water line has to be.

Code Requirements for Water Lines

The standard depth for water lines in the U.S. is around 36 inches, but this can vary from location to location. In Colorado and most other places, plumbing regulations are generally based on the International Plumbing Code (IPC) and the International Residential Code (IRC). 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.

However, it is important to note that this minimum is only applicable to places where the ground rarely or never freezes. 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.

Also known as frost depth, the frost level is how far below ground level the soil could freeze during the winter, i.e., the total depth that frost penetrates into the soil. In the U.S., the frost level is typically measured by taking the average of the three deepest frost penetrations over the last 30 years. Specific frost depth information is typically provided by the U.S. Department of Commerce and the National Snow and Ice Data Center, and local building codes are usually based on this data.

As you can imagine, there is a huge difference in average frost levels across the country. There can also be quite a difference in frost levels within one particular area depending on factors like elevation, terrain, local climate, and soil composition.

While the frost level in the very southern part of the country and along the entire western and southern coasts is typically only around 6 inches deep, some places in the northern U.S. have a frost level of up to 100 inches deep. In the Denver area, the average frost level is somewhere between 40 and 50 inches below ground. That being said, the closer you get to the mountains, the deeper the frost level typically is due to elevation.

Based on an average frost level of 40 inches, water lines in the Denver area will typically need to be a minimum of 46 inches to prevent freezing. However, even though the minimum set out by the IPC is 6 inches below the frost level, most experts recommend that water lines be at least 12 inches below the frost level. This is because the frost level measurement is merely an average, and there is always the chance that frost could penetrate much deeper underground during an extreme cold spell.

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.

If your home is supplied by the Denver Water Department, then the regulations state that all water lines must be at least 4.5 feet underground and can be no deeper than 6 feet below grade. The regulations also state that if you ever raise or lower the ground level in any way, you are legally required to relocate the water line to ensure it is still covered by 4.5 to 6 feet of dirt. These regulations obviously don’t apply if your home has a water well, but your water line will still need to conform to the IPC code.

The fact that frost levels vary so much throughout the Denver area makes it essential that you always hire an experienced, local plumber to install or replace any water or sewer lines as they will know exactly how deep the lines need to be to ensure they won’t freeze. A plumber can also calculate the required depth based on soil composition.

What Happens If a Water or Sewer Line Freezes?

Both frozen water lines and sewer lines can be serious issues. If your water line freezes, at the very minimum, you will likely have to go without water for days or weeks until the pipe thaws out. Depending on what type of pipe is used for your water line, there is also a chance that it could break when it freezes since ice expands and takes up much more room than liquid water.

A frozen water line could easily result in your home being flooded or major damage to your home’s foundation. This is part of the reason why more and more homes now use cross-linked polyethylene, commonly known as PEX, for the main water line instead of PVC pipe. The issue with PVC is that it is quite brittle and prone to cracking or breaking in low temperatures even if the water inside the pipe doesn’t freeze. PEX, on the other hand, is quite soft and flexible and can expand as needed without breaking. PEX also has a greater insulating factor, which means that it is less likely to freeze compared to PVC.

A frozen sewer line can cause huge issues as well. The risk of your sewer line breaking if it freezes is typically less than that of your water line. However, a frozen sewer line will mean that all of the waste and water you put down the drains and toilets won’t be able to flow out into the municipal sewer main or your septic tank. As a result, you will quickly start to have sewage backing up inside your drains and potentially flooding your home if you were to continue using your plumbing when the sewer line is frozen.

How Deep Do Sprinkler Lines Need to Be Buried?

If your home has an underground sprinkler system, all of these lines need to be buried a certain distance underground. The general rule of thumb for sprinkler lines is that they should be at least 8 inches below ground level.

With sprinkler lines, you don’t really need to worry about them being below the frost level. As long as you make sure to shut off your sprinkler system each fall before the first major frost and have the system drained and all the lines are blown out, you shouldn’t ever have to worry about your sprinkler lines freezing and breaking.

If you were ever to neglect to have your sprinkler system blown out, any lines that break wouldn’t be immediately noticeable as long as you shut the water to your system off. However, as soon as you turn the water back on next spring, your yard and potentially your basement or crawl space could quickly start to flood.

At High 5 Plumbing, we can help if you need your water line repaired or replaced or if you need a new water line installed. We can also assist with sewer or gas line services or any other type of plumbing installation or repairs. For more information or to schedule a plumbing service in the Greater Denver Metro area, give us a call today.

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