---
title: Setting New and Old Pipe Condition
description: "# Changing Velocity Equation and its Roughness Coefficient In Sewerage Module, we have different Manning coefficient for the new and old pipe. When pipe ages, the Manning coefficient will change, because the roughness will be changed. This is why we…"
url: "https://mes100.com/docs/sewnet-old-new-pipe/"
updated: "2026-10-07"
category: Sewer / Input / Sewer
---

# Setting New and Old Pipe Condition

# Changing Velocity Equation and its Roughness Coefficient

In Sewerage Module, we have different Manning coefficient for the new and old pipe. When pipe ages, the Manning coefficient will change, because the roughness will be changed. This is why we have two sets of parameter for Manning coefficient (and likewise for Hazen-Williams and Colebrook-White), entered in Options -> Project Settings -> Sewerage -> Material -> Pipe Type.

![](https://i0.wp.com/mes100.com/wp-content/uploads/2026/10/changing-velocity-equation.png?w=1080&ssl=1)

# Setting Sewer Pipe Condition

By default, MiTS analyse both the new and old pipe conditions, as the authority may require both calculations to be submitted. To analyse only one pipe condition:

1. Go to Options > Project Settings > Sewerage > Design
2. Set **Pipe Condition to Analyse** to *New Only* or *Old Only*.

When *New Only* or *Old Only* is selected, design checks (such as the velocity check) use only the coefficients for the selected pipe condition. The other condition’s coefficient columns and results are hidden from the material table (inside the Project Settings), sewer spread inputs, excel report and detailed report. The hidden coefficients are kept, so setting it back to *Both* restores the hidden coefficient and result. Changing the pipe condition setting clears the existing results, so run Execute Analysis again. For a force main, which uses a single Hazen-Williams coefficient, *Both* uses the old pipe coefficient.

![](https://i0.wp.com/mes100.com/wp-content/uploads/2026/10/pipe-condition-to-analyse.png?w=1080&ssl=1)

# Rename “New Pipe” and “Old Pipe” Label

You can rename the “Old Pipe” and “New Pipe” labels, for example to “Existing Sewer” and “Proposed Sewer”. Go to:

1. Options > Project Settings > Sewerage > Pipe Condition Headings.
2. Enter the required label/ heading for the pipe condition.

The headings appear in the material table, sewer spread inputs and reports. Renaming a heading does not affect its coefficients or analysis results. When only one condition is analysed, you can leave its heading blank to omit the label.

![](https://i0.wp.com/mes100.com/wp-content/uploads/2026/10/edit-new-and-old-heading.png?w=1080&ssl=1)

### *Related*

 [![](https://i0.wp.com/mes100.com/wp-content/uploads/2024/10/me-small.jpg?resize=100%2C100&ssl=1)](https://mes100.com/author/admin/)[Ngu Soon Hui](https://mes100.com/author/admin/)

I’m the [Benevolent Dictator for Life](https://en.wikipedia.org/wiki/Benevolent_dictator_for_life) for MiTS Software cum Editor of this website. Read more [here](/about-ngu-soon-hui/).

You can also contact me at soonhui@mes100.com