Albstadt is a town located in southwest Germany, about 80km south of Stuttgart. Albstadtwerke are the utility network distribution provider in this region supplying potable water, natural gas and electricity. In addition to managing and maintaining the local distribution assets in Albstadt, Albstadtwerke operate and maintain two more potable water distribution networks, seven natural gas distribution networks and an electricity supply.
Albstadtwerke is efficiently run with 80 employees for the entire operation and construction of our networks and facilities. It has been a corporate policy for many years to continuously evaluate current methodologies and introduce new innovative methods in leak detection and trenchless pipe installation.
In this paper we will share information about our vast experience with innovative technologies in reducing water loss and information about our latest system that permanently monitors the network and alerts us as soon as a leak appears.
Figure 1 shows a picture of the Albstadt region, which is spread across three valleys and has a height variation of 400m. This geographical landscape creates a number of operational challenges, including:
- A large number of different pressure zones;
- Long sections of trunk main; and
- Long distances for maintenance staff to drive to reach the extremities of the network.
Approximately 50% of the water supply comes from our raw water catchment and is processed in several stages at our water plant to produce high-quality drinking water. The other 50% is purchased from a total of three suppliers. We are about 80km away from the Lake of Constance, which is one of the biggest lakes in Europe.
Our current Non-Revenue Water is 20% (500,000 cubic metres), which has increased from 10% five years ago. The increase in the NRW percentage is due to a 50% reduction in total consumption; our water loss has remained constant.
The ground is limestone, which means that almost no leak is visible on the surface as there is always good drainage. We have had massive leaks of 25L/S disappear underground (Figure 2). Our first investigation was in the Braunhartsberg reservoir zone. This zone consists of 52km of pipework with a mixture of cast iron, UPVC and ductile iron, and it contains most of the factors that make leak detection difficult.
Water Loss Innovations
Our first strategy to improve network efficiency was to install a flow meter on the reservoir outflow and have the data sent to our office on a daily basis with alarms to advise us if there was an increase in minimum night flow (MNF). This is shown in Figures 3. In addition to providing an alarm warning us the MNF was rising, we could also quantify the size of the leak.
Leak detection was performed by sending a team out in a van to deploy
noise loggers with radio communication (Figures 4) and then download the data in a driveby survey the following day to localise the leak position and use a ground microphone and correlator to pinpoint the leak. We have been using this equipment for many years and we have found that only loggers with radio communication could be used efficiently. The loggers are mounted directly on the pipeline with a magnetic connection to provide a good sound recording. It would often take this two-man crew five to ten days to find the leak in this large zone, driving an hour each way every day.
The next strategy made to improve efficiency was to install additional flow meters within the zone to localise the leak position to a smaller area within the zone, and reduce the amount of time spent searching for the leak.
We were not measuring or analysing total flow into sub-zones, we were just looking at significant changes in daily water flows to localise the leak positions.