Assessing boundary valve water tightness
asked 7 September 2016 asked by SeineOiseMarne ( points)
Hello, Both options are valid, but the second is more "quantifiable" because it doesn't involve relying on the detection abilities of the technician doing the listening. The most reliable method is to perform true water stoppage: it's burdensome but a sound investment in the long run. You avoid time spent searching out a leak in water volumes that flow into another district. In terms of infrastructure maintenance, it is also a good opportunity to refurbish older valves, an investment that will pay for itself if ever there is a significant breach in the network. Sincerely,
Hello, totally agree with fredlock. It's a chance to review and update the network layout and identify any pipe gridirons you aren't aware of.
You can also use a device like the Sewerin Aquaphon, which allows you to listen to valve noise in real time. This way, you don't waste time waiting for the data logger results, and it is a more sophisticated acoustic detection technique than just listening at the valve actuator.
Good answers from all. Some additional thought. Agreed that a shutdown test is the best initial proof of valve water-tightness on a valve-by-valve basis, but eventually you will need to put in place the boundary of the new District Metered Area (DMA), which should have one or maybe two supply pipelines open to feed the area. Once the new boundary is is initially put into place, place pressure loggers on fire hydrants near the boundary, with one inside the area boundary, and another on a hydrant nearby just outside of the boundary. You can install several matched pairs of loggers in this manner at different points around the boundary. Now generate a high water demand in the DMA by opening one or more fire hydrants. Observe the pressure changes at the loggers. The high water demand will cause a reduction in pressure in the loggers that are inside the boundary. However, the loggers outside of the boundary should see no change in pressure if the boundary is water-tight. If any of the loggers outside of the boundary record a pressure drop, the nearby valve is likely not water-tight and is "passing" water into the DMA toward the high water demand. Sound the valve to see if you can confirm this via sounding. Valves that "pass" water (are not water-tight) can sometimes be improved by repetitive exercising of them (open and closed positions) as water is flushed to a nearby fire hydrant to remove any debris coming from the valve. Unfortunately, valves in many systems are very old and have not been exercised regularly and will require replacement to create a tight DMA boundary. By doing this pressure test - with successful results - the DMA can be confirmed as having water tight boundaries.