Step testing procedures are performed to determined exact leakage volumes. In the case of larger supply networks as municipalities water network with several DMA’s, Aquasave can undertake a Step Test to isolate the area(s) of leakage, as opposed to surveying the whole system in detail, therefore reducing the time on site, and the associated costs. This technique requires use a series of short steps isolation of sections of pipe by closing the line valves one by one. During the test, the flowrate through the water meter or temporary meter such as mobile ultrasonic meter (which do not interfere with normal system operation) is observed and the times when each section of pipe is isolated is noted. A large decrease in flow, or “step”, indicates a leak in the section of pipe which has just been isolated. This technique enabling to see the results of the valve closure immediately, speed up the operation, and reduce the time the valves are left closed.
This technique, mostly on municipality’s water network, is usually undertaking during the night hours in order not to interrupt the regular supply of water to the customers. The minimum night flows are evaluated against expected and calculated legitimate usage within that DMA. If there is certainty that there is sufficient leakage for that DMA, Step Testing will be performed within that DMA to localize any leakage potential. After each section closure, re-evaluation of the recordable night flows is conducted to see if the amount of estimated leakage is found. This allows for quick and immediate decision making by the client in order to control the costs of the leakage survey. Estimated leakage potential within each isolated DMA and each subsection within that DMA will be known.
The Step Test also provides an effective way of checking traditionally hard to find leak situations such as PVC systems.