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AltPipe is a web-based tool that may be used to assist designers in the appropriate selection of pipe materials for culvert and storm drain applications. The computations performed by AltPipe are based on the procedures and California Test Methods described in Chapter 850 of the Caltrans Highway Design Manual.

AltPipe is not a substitute for the appropriate use of engineering judgment as conditions and experience would warrant. AltPipe establishes uniform procedures to assist the designer in carrying out the highway design functions of the California Department of Transportation, and is neither intended as, nor does it establish, a legal standard for these functions. Implementation of the results and output of this program is solely at the discretion of the user.

Altpipe Layout

Altpipe uses 3 different pages.

  1. Project, Structural, Corrosion and Abrasion, and Hydraulic Information
  2. Pipe specific selection and estimated service life.
  3. Final overview for printing.

Project, Structural, Corrosion and Abrasion, and Hydraulic

The first page is set up to gather information that will be used on the second page to narrow down the selection of available pipes.

Project Information

The first section asks for some basic information about the project that will be printed with the pipe information.

Structural Requirements

This section asks you to identify the pipe by ID. Note: Each pipe entered into Altpipe must be unique. Using the same ID will cause you to overwrite the previous information. Typically the the drainage system number/letter used on the plans is entered, e.g., 5a. You will also be asked to select the pipe's diameter and input the maximum height of cover.

Corrosion and Abrasion Conditions

This section asks you to select the design service life of the pipe, and input the worst case of either soil or water pH, minimum resistivity, sulfate and chloride concentration, and select the abrasion level. This information is used to determine if a pipe material will give a long enough service life. In this section you are also asked to select the abrasion level and input the 2-5 year storm flow velocity. The velocity must be within the allowed values for the selected abrasion level. Note that abrasion Levels 1-3 are non-abrasive and higher velocities may be applicable.

Pipe Specifics

The second page gives estimated lifetimes for various pipe materials. You will be able to change pipe thickness and other information in order to meet your design service life. Values that meet your design service life will look like this. The page is broken up by pipe material.


Steel pipes are used as the baseline for the other pipe materials. In the steel section you will be able to adjust the estimated loss of steel due to abrasion. If other pipes in the region have shown more or less wear than what is listed you may adjust the value. The other pipe materials will be recalculated based on this new value.

In the steel section there will be a table with the estimated service life of steel pipe and various abrasion coatings. To meet the service life requirement you can adjust the steel thickness. This will cause the service life values to be recalculated.

The program calculates no additional loss of steel due to abrasion for Level 1 through Level 3 because it is assumed California Test 643 already incorporates some unknown loss due to abrasion. The wear rates for additional loss of steel due to abrasion for Level 4 through Level 6 were developed from a combination of field testing and a limited statewide field data set. See Appendix E, 'Evaluation of Abrasion Resistance of Pipe and Pipe Lining Materials' Final Report, Federal Study # F 2001 OR 12.

When available, it is highly recommended to use local steel wear rate data (for similar diameter pipes) based on original thickness and estimated time to perforation or through actual thickness measurements using ultrasonic measuring equipment to determine the appropriate abrasion level. Generally, the higher abrasion levels do not apply for pipes 30" or smaller in diameter and abrasion Levels 2 or 3 may be used for higher velocity ranges if significant wear from abrasion is not apparent even with larger bedloads than sand.

Reinforced Concrete Pipe

The RCP section allows you to adjust the amount of concrete cover over the steel reinforcement and the amount of cement used. The estimated service life for RCP will be recalculated if you change the amount of cover or cement. Per discussions with industry, you need to follow the steps outlined on the worksheet page when changing the cover or cement values.

Note that RCP is not recommended for abrasion levels 4 through 6 and RCB is not included in AltPipe. See Appendix E, 'Evaluation of Abrasion Resistance of Pipe and Pipe Lining Materials' Final Report, Federal Study # F 2001 OR 12.


When the soil or water pH and resistivity is within the allowable range (5.5 and 8.5, inclusive and 1500 ohm-centimeters or greater) aluminum will be listed as a viable alternative to steel. However, aluminum is genarally limited to abrasion levels 1 through 3 which are non-abrasive in AltPipe.


In low to medium abrasion environments (i.e., abrasion levels 1 through 4) plastic pipes will be listed as alternatives. For both PVC and HDPE the estimated loss due to abrasion will be listed.


After submitting your pipe details Altpipe will look for pipe materials that meet your specifications and stores the results until you are ready to view the final summary.

Summary Page

After submitting your pipe details you will be taken back to the first page in order to add another pipe if you wish. However, if you are done adding pipes you can use the link at the top of the page to go to the final summary page.

On this page each pipe you specified will be listed in seperate columns. The various pipe materials are listed by row. Due to browsers not handling tables across pages very well we suggest that you do not input more than 10 pipes before clearing.

Other Information



I am a warning box. When you see me please stop and think. I have important information that should be read and followed. Failure to do so may cause unexpected results.

Service Life

In order to aid you in easily determing when a material meets the service life requirement the values will have a seperate style to them.

For example:


AltPipe makes use of default values when the user does not enter a value or change the value from the initial value.

Pipe Diameter

Defaults to 12 inches. This is simply the lowest value of a pipe diameter from a range with a maximum input value of 252 inches. See the HDM or follow District policy to verify minimum pipe diameter for various situations.

Design Service Life

Defaults to 50 years. Topic 852.1 of the Highway Design Manual discusses the design service life for drainage facilities for all projects. Typically the value is either 50 years or 25 years. AltPipe provides the user with a range from 5 to 50 years.

Abrasion Level.

Defaults to level 1. Levels 1 through 3 are "non-abrasive" with no additional material thickness added for service life calculations. See "AltPipe and Evaluation of Abrasion" in the "Get more information" page.


Defaults to 20000 ppm.


Defaults to 25000 ppm. If the measured concentration of chlorides exceeds 2000 ppm two checkboxes will appear to specify if the RCP is placed in brackish or marine environments and where the high tide line is below the crown of the invert. If both boxes are checked, a default value of 25000 ppm is assigned (worst case corrosion conditions).

Please remember

The following alternatives are not included in AltPipe and will not be provided in the output Alternative pipe list: all non-circular shapes (arches, boxes etc), non reinforced concrete pipe (NRCP), non-standard new pipe products including pipe liners. Check Materials and Hydraulics reports and verify if any of these alternatives were recommended and supplement the AltPipe final summary accordingly.


This program doesn't have a brain so make sure to use yours!

AltPipe Version 7 © State of California