Historical values of Unaccounted for Water (UAW) for Topsfield are listed below. Beginning in 2006, DEP requires UAW be kept below 10%. We were able to do this for several years but in 2009 UAW jumped to 11.5% despite annual leak detection surveys. We conducted an extra round of leak detection during Fiscal Year 2010 & 2011 to compensate for the increase.
We lost 7.16 million gallons of water during 2011 or 13.6 gallons per minute. If the leakage were the only reason for the loss, we would be looking for a single hole slightly less than 5/16 inch diameter or up to twenty-four 1/16 inch leaks. Large leaks are easier to find because the water will surface or the noise created by the water escaping from the pipe can be heard by a trained leak detector with the proper equipment.