Leak detection on Bornholm
The rock carries the sound further than the distance suggests
The bedrock lies close below the surface in large places on Bornholm, and the pipes are laid where there is space: in natural crevices or in thin layers of soil on top of solid rock. This gives a sound image that does not behave like in sandy soil.
Solid rock conducts sound far and with little attenuation. A strong signal in a valve well can therefore originate from a leak a good distance from the point where you are standing, and an operator who does not know the subsurface will end up pointing incorrectly.
What bedrock means for leak detection on Bornholm
We don't let one listening point decide the matter. The signal is measured at two points, and the position is calculated from the time difference between them, so the distance is based on a calculation rather than an assessment of how loud it sounds. The method is strongest on long, straight stretches, and there are some of these between the towns on the island.
The rock also affects the water. If water flows into a crevice, it moves along the rock until the crevice gives access to the surface, and the moisture therefore appears in a completely different place than the hole. A wet spot on the side of the road is an even worse indicator on Bornholm than in sandy soil.
If the sound image is still ambiguous, we switch to tracer gas. Harmless gas is injected into the pipe, and the surface is scanned afterwards. The gas comes from only one place, and the acoustics of the rock therefore play no role in the result, which lands with an accuracy of a few centimeters.
July puts more pressure on the network than February
Summer consumption on Bornholm is far higher than winter consumption, and this changes what a leak means. A loss that is tolerable in February can cost pressure at the ends of the network, where the summer homes and campsites are located, during the peak season.
The season also hides the loss in the statistics. When the water pumped out increases sharply from May, a constant loss disappears into an increase that everyone expects, and a waterworks may end up explaining the entire difference with the guests. Only when autumn sets in and consumption does not fall back completely, the loss becomes visible again.
This speaks in favor of measuring outside the season, when consumption is low and the nighttime noise picture is quiet. But it also speaks in favor of having data loggers sitting in the net over the summer, where they listen around the clock, and where HydrantAI automatically alerts if consumption patterns change faster than the season can explain.
Leak search on Bornholm planned from the back
An operator who is going by ferry or plane will not just leave again tomorrow. That is why we put the task in reverse: first we agree on what needs to be measured when the visit is over, and then how many days it will take.
It also changes what needs to be taken with you. The equipment for acoustic measurement and for tracer gas comes on the same trip, so the change of method can be done on site instead of having to pay for a new trip. If there is a suspicion that the map material is not suitable, we plan wire search into the same visit.
Before the trip, we review the map material and measurement setup with you, so that it is known in advance which wells and valves can be opened, and who has the key. The search is carried out from the surface and from the network's existing measurement points, so there is no need to block off or dig along the way, and a review can therefore be scheduled in the middle of an operating week. This is also why several water utilities can advantageously coordinate a joint visit — the drive between two small networks on the island is short, and the days are spent on measurement instead of transport.
When the equipment must stay on the island
Some networks need a review once a year. Others need to be able to screen themselves between visits, especially when the distance to the mainland makes each call a planned action. Search equipment can be purchased or leased from us with service by agreement, and that makes a difference here: if an instrument stops, it will have to be taken by ferry to the mainland before anyone can measure again. We are an authorized distributor of, among other things Gutermann.
If your own operator is to be able to use it sensibly, he can take a basic course in wiring and leak detection at DWI Leak Academy in Hørsholm, where the theory is followed by exercises on a test track. Then the first assessment is made locally, and we are called in for what requires more.
Yes, but the sound image must be read differently. The rock carries the signal a long way, so the strength alone does not say much about the distance. We use correlation between two measurement points and switch to tracer gas, where the sound cannot carry the conclusion.
By planning access first. We agree on the measurement setup and access before arrival, and we allocate enough days for the entire route. What cannot be reached, we agree in advance will be the next stage.
It depends on how much pressure it takes during the peak season. If it is felt at the ends of the network, it should be found now, and in the case of acute breaks, we often respond the same day. If the loss is small and stable, the review can be advantageously scheduled for the fall, when the sound picture is calmer.
Yes, and it is often the cheapest way to have an island network measured. We make a comprehensive plan for the days and report on each waterworks separately.
This makes good sense. With your own equipment and a basic course, you can find the obvious losses yourself and determine which section needs to be looked at more closely before you call.
Contact DWI
Contact us for competent advice, leak detection and pipe location for your waterworks or water supply. We also assist commercial customers and private households with professional solutions.
