How deep does a sewer line have to be in Colorado?

What does the plumbing code say about sewer depth?

The model plumbing code (IPC Section 305.4.1) sets a minimum depth for building sewers, but it leaves the number blank. There are two blanks: one for the depth at a septic tank connection and one for the depth everywhere else. Each city or county writes its own numbers into its adopting ordinance.

So the model book alone can’t tell you how deep to dig. You need the local number.

Why is sewer depth different in every Colorado city?

Cities set the depth for their own conditions: frost, soils and how their sewer mains are laid out. A town in the mountains and a suburb on the plains can land on very different numbers, even a few miles apart.

Sewer depth is a separate number from frost depth. Frost depth governs water lines and footings. See water line depth by city.

Which Colorado cities set their own sewer depth?

32 of the 41 jurisdictions in the app have a local sewer depth rule. Where the rule is already a free sample on the city’s page, it’s shown here (14 cities). The rest are in the app.

What about a septic tank connection?

The code has a separate depth for a building sewer where it connects to a septic tank. Some cities fill in both numbers, and some use one number for both. The app shows both when a city sets them.

How do I show a customer the rule?

Pull up the city’s rule on your phone and show the section and ordinance right there in the driveway. See Sell with Code.