Water & Sewage Mapping
Water and Sewer Network Mapping:
Turning Paper Records and
CAD Drawings into Reliable Asset Data
You cannot maintain, plan or repair a pipe network you cannot locate. Here is what a good water and sewer map contains, how legacy records are converted into it, and what to agree with your mapping partner before work starts.
Key takeaways
- Most water and sewer networks were built over decades, and their records often sit in mixed formats: paper as-builts, scanned plans and legacy CAD files.
- A useful network map is more than lines on a drawing. It links each pipe, valve and manhole to attributes such as diameter, material and levels.
- CAD and GIS do different jobs. Many utilities need clean CAD drawings first and a GIS database as the end result.
- Good mapping flags what is uncertain instead of guessing, and checks that the network connects properly before it is delivered.
Why records are the weak link in an ageing network
Pipes, manholes and valves are buried, so the map is often the only way anyone knows where they are. When that map is a stack of paper drawings, a scan that has never been georeferenced, or a CAD file with no attribute data, everyday decisions get harder: which main to inspect first, which valves to close during a repair, which sections to renew within a limited budget.
The wider picture explains why this matters. In its 2025 Report Card for America’s Infrastructure, the American Society of Civil Engineers graded drinking water C- and wastewater D+, both unchanged from 2021, citing ageing pipes and facilities and unsustainable financing as major obstacles. The US Environmental Protection Agency notes that the country has roughly 20,000 separate sanitary sewer systems, each with its own records and its own history.
These are national figures from US sources. They illustrate the scale of the challenge rather than describe any one utility. Networks in the UK, Australia and elsewhere face similar issues of age and incomplete records, but the grading and counts above apply to the United States.
Water main breaks per 100 miles of pipe per year (US and Canada)
Source: Utah State University, Water Main Break Rates in the USA and Canada: A Comprehensive Study (completed December 2023), as reported by Trenchless Technology. Bar lengths are proportional.
The study reports a 20% drop between the two editions, and attributes falling break rates in older cast and ductile iron pipe to the worst-performing pipes having been replaced. That is a useful reminder of what mapping is for. Renewal is only as targeted as the data behind it: a utility that knows the material, age and location of every main can choose which pipes to replace first. One that does not is working partly blind.
What a good network map actually contains
A drawing that shows where a pipe runs is a start. A network map also records what each asset is and how it connects. The exact schema depends on your standards, but most projects cover the following.
| Asset | Typical information captured | Why it is used |
|---|---|---|
| Water mains and service lines | Diameter, material, installation year, status, owner | Repair planning, renewal programs, hydraulic modeling |
| Valves, hydrants and meters | Type, size, location, identifier | Isolating sections during repairs, flushing, operations |
| Gravity sewer mains | Diameter, material, flow direction, upstream and downstream manholes, invert levels | Capacity checks, inspection scheduling, blockage response |
| Manholes and chambers | Rim level, invert levels, depth, cover type, identifier | Inspection, access, survey verification |
| Force mains and pump stations | Diameter, material, pump details, connected network | Operations and emergency planning |
| Laterals and connections | Location, size, connected property or network point | Connection records, new development, enquiries |
The records we convert
Almost every utility has a mixture of sources. A mapping project usually starts by sorting what exists and deciding which is most reliable.
Paper as-builts and scans
Hand-drawn or printed plans of installed pipes and chambers, often at varying scales and conditions.
Legacy CAD files
DWG and DGN drawings that show geometry but lack coordinates, consistent layers or attribute data.
Spreadsheets and registers
Asset lists that hold diameters, materials and dates, but are not linked to a map.
Survey and field data
GPS points, survey coordinates and inspection notes from site work that need placing into the network.
Where on-site scans are available, such as laser scans or Matterport captures of pump stations and chambers, they can also be converted into drawings. See our guide to outsourcing point cloud modeling and conversion.
CAD or GIS: which does your network need?
The two are not competitors. They answer different questions, and many projects use both.
| CAD network drawing | GIS network database | |
|---|---|---|
| Main strength | Precise drawings for design, construction and as-built records | Queryable asset data with location, relationships and attributes |
| Typical use | Project drawings, extensions, repairs, tender documents | Asset registers, planning, reporting, field apps and maps |
| How data is stored | Lines, symbols and text in layers | Features with attribute tables and defined connections |
| Best when | You need accurate drawings of what is installed | You need to search, analyze and report across the whole network |
A common route is to clean and complete the CAD drawings first, then convert them into GIS features with consistent attributes. Our guide to paper map to GIS conversion covers the accuracy side of that step in more detail.
How a network mapping project typically runs
- Standards and scopeAgree the coordinate system, layer or feature naming, attribute list and delivery formats before any drawing begins.
- Source review and georeferencingRecords are sorted by reliability, then positioned using survey points, base maps or other agreed references.
- Digitizing and draftingPipes, manholes, valves and structures are drawn or digitized from the sources, with annotations carried over.
- Attribute captureDiameter, material, year, levels and identifiers are entered from the records and linked to the right assets.
- Connectivity and quality checksThe network is checked for gaps, overshoots, duplicates, reversed flow direction and missing attributes.
- Delivery and query listYou receive the finished data in the agreed formats, plus a list of items needing field verification.
Common problems in legacy records, and how they are handled
| Problem | Sensible approach |
|---|---|
| Missing diameter, material or year | Leave the field flagged as unknown rather than estimating, and add the asset to the verification list. |
| Two records disagree on the same pipe | Apply the agreed hierarchy of sources, and record which source was used and why. |
| Plans in a local grid or without coordinates | Georeference to survey points or a base map, and note the expected positional accuracy. |
| Overlapping drawings from different decades | Resolve to a single network and keep the original drawing reference as an attribute. |
| Manhole levels not recorded | Leave blank and flag for survey. Do not interpolate values that will be used for capacity analysis. |
| Pipes that do not connect on the drawing | Fix obvious drafting gaps, and query genuine breaks in the network with the client. |
The principle behind each row is the same: a map that shows its uncertainty is more useful than one that looks complete but hides guesswork. Engineers can act on a flagged gap. They cannot easily detect a hidden one.
Why connected, attributed data is worth the effort
The EPA publishes guidance on an asset management approach for sewer systems, and the settlement requirements it summarizes show where records fit in. In the Baltimore settlement it describes, the city must investigate its entire collection system, install a computerized system model and run an information management program. Those requirements depend on having a reliable map of what exists.
Even without a legal driver, the benefits are practical: faster response when something fails, better evidence for renewal budgets, and fewer surprises when new work starts near existing pipes. Mapping consultants, engineering firms and contractors who need accurate utility drawings for design work gain the same advantages.
Who commissions water and sewer mapping
Municipalities and councils
Digitizing archive plans so the whole network can be searched, reported on and shared across departments.
Water and sewer utilities
Building a consistent asset register from drawings that were produced under different standards over many years.
Engineering consultants
Adding drafting and GIS capacity for studies, masterplans and network upgrade designs.
Surveyors and contractors
Turning field survey data and utility records into clean drawings for design and construction.
Questions to ask a mapping partner
| Question | Why it matters |
|---|---|
| Can you work to our schema and naming standards? | Data that fits your existing system needs far less clean-up on delivery. |
| How do you handle missing or conflicting data? | Look for flagging and a query list, not silent assumptions. |
| What connectivity and quality checks do you run? | Networks should be checked for gaps, duplicates and flow direction before handover. |
| Which formats can you deliver? | Confirm CAD, GIS and any exchange formats your team or software needs. |
| Can you work in batches and report progress? | Large networks are best delivered area by area so you can review early. |
| How will our records be protected? | Utility network data is sensitive infrastructure information. |
DigitiseIT has been providing CAD and GIS expertise to global customers for over 25 years. We support utilities and consultants through our Water & Sewage and GIS work, alongside CAD drafting. For the wider picture on infrastructure drafting, see our article on utility and infrastructure modeling.
Have water or sewer records that need converting?
Send a sample of your plans, scans or CAD files and tell us the end format you need. We will review the sources and come back with a scope and quote before any work starts.
Related articles
References
- American Society of Civil Engineers, 2025 Report Card for America’s Infrastructure, drinking water and wastewater grades (C- and D+, unchanged from 2021). infrastructurereportcard.org
- Utah State University, Utah Water Research Laboratory, “Water Main Break Rates in the USA and Canada: A Comprehensive Study” (2023), reported in Trenchless Technology: 11.1 breaks per 100 miles per year in 2023, down from 14.0 in 2018. trenchlesstechnology.com
- US Environmental Protection Agency, sanitary sewer overflows fact sheet (archived copy): roughly 20,000 separate sanitary sewer systems in the United States, and a summary of the Baltimore settlement requirements. epa.gov (archive)
