Best Practice for Asset Condition Assessment of Water and Wastewater Utility Pipes

A two‑tiered approach is the most practical and defensible method for assessing linear assets.

Most utilities struggle with the same challenge. They own thousands of feet of buried pipe, but only a fraction of it is visible, measurable, or easily inspected. Senior managers and board members want defensible decisions about renewal and replacement, yet the data is often incomplete or inconsistent. The most practical solution is a two‑tiered approach that uses GIS data to screen the system and then focuses a detailed assessment on the highest‑risk segments. This method is efficient, cost‑effective, and increasingly recognized as the best practice.

From the Real World

“So, do you feel better about the condition of your linear assets or your vertical ones?” I asked the asset manager.

“Definitely the linear assets,” he replied. “We have a really aggressive cleaning and CCTV program. We know where the questionable pipes are.”

So, where are your condition assessment scores? In the GIS or in the EAMS, I don’t really see a comprehensive list? I asked.

We really haven’t completed converting all the CCTV work into PACP scores,” he replied.

PACP scores are the standardized condition ratings used in North America to evaluate the structural and operational condition of sewer pipelines based on CCTV inspections. PACP stands for Pipeline Assessment Certification Program, developed by the National Association of Sewer Service Companies (NASSCO).

“And doesn’t CCTV only apply to gravity sewer lines?” I asked, but already knew the answer.

“The pressured water lines and the sewer force mains are very expensive to evaluate, as you know,” he calmly stated. “We haven’t gotten to prioritizing or doing those yet.”

It’s not an uncommon story. The utility understands its pipelines relatively well through experience and normal operating procedures. However, the formal condition assessment scores are missing, and worse, some of the most critical pipes have not been prioritized or assessed.

Overview of Collection and Distribution System Piping

Linear assets form the backbone of every water and wastewater utility. Distribution systems deliver treated water to customers. Collection systems convey wastewater to treatment facilities. Both systems rely on a mix of pipe materials, diameters, and installation eras. These differences matter because each combination of material, size, and age carries its own failure modes and service life expectations.

Water distribution systems often include ductile iron, PVC, cast iron, and HDPE. Wastewater collection systems typically include vitrified clay, ductile iron, PVC, and reinforced concrete. Diameters range from small service lines to large transmission mains and trunk sewers. Installation dates may span more than a century. This diversity makes a one‑size‑fits‑all condition assessment unrealistic. A structured, tiered approach is essential.

Two Levels for a Practical Approach

A practical condition assessment program for linear assets has two levels. The first level is systemwide screening that uses existing data. The second level is a targeted, field‑intensive assessment of the highest‑priority segments.

Old pipes are necessarily in poor condition.

The first level answers a simple question. Based on what we already know, which pipes deserve closer attention? The second level answers a deeper question. What is the actual condition of those pipes, and what actions should we take?

This structure keeps the utility from wasting resources on low‑risk assets while ensuring that the highest‑risk segments receive the detailed evaluation they require.

Condition Assessment Screening Using GIS

Most utilities already have the information needed for the initial assessment. GIS contains pipe material, diameter, installation year, and location. These attributes allow utilities to create a screening score that highlights segments with the greatest likelihood of failure or the greatest consequence if failure occurs.

Material is a strong predictor of failure mode. Older cast iron behaves differently from PVC. Vitrified clay has different risks than ductile iron. Diameter influences both failure consequence and replacement cost. Age provides a proxy for deterioration, especially when combined with known service life ranges.

GIS screening is fast, inexpensive, and repeatable. It allows senior managers and board members to see the systemwide picture and understand where risks are concentrated. It also provides a defensible basis for prioritizing more detailed assessment work.

Condition Assessment Scoring Using Field Tools

The second level of assessment focuses on the highest‑priority segments identified in the GIS screening. This level uses field‑intensive tools that provide direct evidence of pipe condition. These tools are more accurate and also more expensive, which is why they should be applied selectively.

Gravity sewer condition is often evaluated with CCTV scoring. Standardized scoring systems allow utilities to compare defects across the system and track deterioration over time. Pressure pipe condition is assessed with technologies such as acoustic testing, pressure transient monitoring, or electromagnetic inspection. Other tools include soil corrosivity testing, leak detection, and structural evaluation.

The goal of this level is not to inspect every pipe. The goal is to confirm the condition of the most critical segments and develop actionable recommendations for renewal, rehabilitation, or monitoring.

Say What?

The information I had been provided implied that 70 percent of the condition assessment were complete. This was good news for this large utility with several thousands of miles of pipeline. All we had to do now was fill the gaps.

“Well, it’s not that good,” explained the utility’s project manager. “That’s what we told the State and EPA, but it’s been done over several decades. The quality and consistency of the condition ratings are not good.”

“Say what?” I replied.

“They never asked, so they probably don’t care,” he said. But we know, and we need this to be right.”

We proceeded with a plan to re-screen everything with a GIS-based model and called the new data “condition assessment Index.” Although we tried to use the historic condition ratings as much as possible, the quality and consistency of the data were indeed poor.

Falling back to a two-phase approach ultimately saved us time and money, validated the scores, and saved us frustration finding the poor data midway in the process.

Best Practice for Decision Makers

A two‑tiered approach is the most practical and defensible method for assessing linear assets. GIS screening provides a broad, systemwide view. Field assessment provides detailed, segment‑specific insight. Together, they support better decisions, more predictable budgets, and clearer communication with governing boards.

Senior managers and board members do not need perfect data. They need a structured process that uses the data they have, focuses resources where they matter most, and produces recommendations that can be explained and defended. The two‑tiered approach delivers exactly that.

---

JD Solomon Inc. provides solutions for program development, asset management, and facilitation at the nexus of facilities, infrastructure, and the environment. Visit our Asset Management page for more information related to reliability, risk management, resilience, and other asset management services.