Rapid Leak Detection
Leaks in pipelines are a major cause for water losses. While bursts are usually detected immediately, both by the sudden drop in pipeline pressure and by phone calls from concerned citizens, small leaks are very hard to come by – and can lead to a lot of damage if not discovered and fixed rapidly.
Little Leak - Big Headache
It's the small leaks that cause the trouble. Losses of a few cubic meters per day don't show on the surface. They only show on the monthly bill respectively in the production statistics, when comparing production volume to volume sold. And then it still might have been consumption through unmetered hook-ups, such as fire hydrants, and not a leak.
Detecting such a small leak usually takes many months. Experiences from Austrian and German water providers have shown that it takes at least 6-7 months to detect a small leak. During that time water loss can be tremendous. In a large distribution pipeline, usually pressurized with 10bar, a tiny leak of only 0.5mm² results in an annual loss of 250m³. But as the leak grows over time, so does the loss. At 5mm² the water losses accumulate to more than 15.000m³ per year!
Wasted energy, excessive pump runtime, wasted chlorine and UV lamps
Even the water lost needs to be purified and pumped. Pumping takes power, be it electricity, be it Diesel oil. Pumping wears down the pump and reduces its lifetime. And it takes a while to pump 15.000 m³! And purifying lost water, be it by chlorination, be it via UV lamps, is again a waste of resources.
And if that little leak is never taken care off – it might eventually lead to a burst, and then it gets even more expensive. So can those little nuisances be detected? The ADCON Consumption Profiling system provides the answer!
Up front please let us define the terms used: when we talk of leak detection we do not refer to pinpointing the exact location of a leak. This is usually done by means of a listening device, which is manually moved along the pipeline. Given the length of municipal distribution pipelines, often several 1.000 kilometers, this can be quite a time-consuming effort.
Consequently ADCON defines leak detection as the identification of the pipeline section, in which a leak has occurred through the creation of a consumption profile.
Bulk Meters in Pipeline Segments
Most distribution pipelines are divided into segments, each of which serves a certain type of customer, be that an industrial facility, a large public building or a residential area. The water that flows through each segment is monitored by a bulk water meter installed at the branch-off.
The Consumption Profile
For many years already these bulk meters have either pulse outputs or Modbus interfaces, both of which can be connected to an ADCON RTU. These outputs are continuously monitored, and every 15 minutes the sum of pulses is stored, or a 15-minute total retrieved from the meter via a Modbus command. With these 15-minute totals the water provider has two very valuable pieces of information at hand:
- At which time of the day how much water is needed.
- What is the "night time low"?
The little screen shot top right shows two graphs at the same time: while the purple line shows the level of the reservoir, as water is taken out and it is continuously being refilled, the blue line shows the water consumption in m³. The red line near the bottom indicates the standard night time low for this section.
Analyze the profile - detect the leak
For leak detection it's exactly this night time low that counts. It usually drops to the same level every night. Should all of a sudden the night time low be higher than normal this is good reason to watch. Maybe someone just filled his pool overnight, or a fire had to be put out. Then the night time low will drop back to its usual level the next night. But if it stays at the elevated level, even for a third night, then there is a leak. A parallel shift in the night time low is an unmistakable sign for a leak in the amount of the shift. In the screen shot top right you can see a leak that was immediately detected and repaired on day three. The green line indicates the normal night time low, the red line the new low after the leak had occurred.
The larger screen shot top right in contrast shows a burst. As the pipeline bursts, consumption increases excessively fast, washes away the road, and someone alarms the water company. The pipeline is shut off, the leak repaired, and all is well - easy. The little ones are the tricky ones!
Get an alarm from the system
To make it even more convenient you can set an alarm in addVANTAGE Pro. The condition would compare the usual night time low, e.g. at 2am, with the real consumption at this time. Should this consumption exceed the standard night time low by a user-set percentage, the system will automatically send an alarm message.
Set the ADCON consumption profiler up well, and most leaks can be detected almost over night!
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