Case Study: Leak Detection in Fernwärme Ulm's District Heating Network
How do you find leaks in more than 200 km of district heating network without digging on suspicion? Fernwärme Ulm used drone thermography: 647 findings, 2 major leaks, both repaired.
Thermal district heating network inspection
647 geo-referenced findings, two major leaks, both located and repaired: Fernwärme Ulm GmbH inspected its district heating network of more than 200 km with FairFleet using drone thermography. Instead of searching section by section on the ground, every anomaly in the network appeared on a single digital map. Here is how the project worked and what other network operators can take from it.
The challenge: make-up water shows that water is lost, not where
Every network operator knows the signal: the make-up water volume rises. Somewhere in the network, heating water is escaping, and heat is lost with it. The meter, however, does not reveal where along the route the leak is.
District heating pipes run under asphalt, pavements and green spaces. Conventional ground-based detection works through the network section by section and often needs several exploratory excavations before it finds the leak. For a network of more than 200 km, a full ground survey is barely feasible.
Public scrutiny adds to the pressure: since 2021, German district heating suppliers have been required to publish their network losses under the AVBFernwärmeV regulation (Section 1a). Losses are no longer just a cost issue, but also a reputational one.
The approach: three steps, minimal effort for network operations
Route data in. Fernwärme Ulm supplied the pipe routes as GIS data. From this, FairFleet planned automated flight paths along the pipelines.
Night flights over the network. Measurements were taken in the heating season after dark: cold surroundings, high supply temperatures. Under these conditions, heat losses stand out most clearly in the thermal image.
Central analysis at FairFleet. Pilots capture raw data only. Detection, classification and prioritisation of anomalies run in a standardised process on the FairFleet platform.
For network operations, the effort stayed low: provide route data, review the results, excavate where it counts.
The result: 647 findings, two major leaks
Metric | Value |
|---|---|
District heating network surveyed | more than 200 km |
Geo-referenced findings of thermal anomalies | 647 |
Major leaks located and repaired | 2 |
Not every thermal anomaly is a leak. That is exactly why prioritisation matters: it shows network operations where digging pays off. Fernwärme Ulm was able to pinpoint and repair both major leaks without speculative excavations.
The platform: the entire network on one digital map
All findings sit on the digital network map in the FairFleet platform, located precisely on the pipe route instead of scattered across individual images. Each finding shows the thermal image with measured values and a severity rating.
Prioritised: Network operations see at a glance which findings to check first.
Collaborative: Colleagues, civil engineering contractors and partners can be invited at no extra cost to review the data together. Tasks can be assigned directly.
Comparable over the years: Every survey is stored. Follow-up flights show what has changed.
Evidence at the click of a button: PDF export for supervisory boards, committees and network loss reporting.
Data in the EU: Stored in Germany, never shared with third parties.
The customer's view
“From the 647 findings, we were able to pinpoint two major leaks and repair them immediately. An extremely efficient method for our maintenance.”
Patrick Ruf, M. Eng., Head of Network Construction and Operations, Fernwärme Ulm GmbH
What other network operators can take from it
A drone survey makes an entire district heating network visible in a short time and shows where digging pays off. It saves exploratory excavations, reduces network losses and provides solid evidence for committees and disclosure obligations.
The window for this is the heating season: thermography delivers the clearest images when it is cold outside and the network is under load. FairFleet is now scheduling surveys for winter 2026/27, whether for a section with conspicuous make-up water or for the entire network.
Request a survey of your network: Alexander Engelfried, Managing Director, fairfleet.com
FairFleet is Europe's largest drone platform, with more than 1,000 customers and over 65,000 completed projects. All data is processed and stored in Germany.