Each year we report the the Massachusetts Department of Environmental Protection how much water was used per person per day.  Topsfield residents that rely on teh public water system 50.5 gallons per day per person during calendar year 2010.  We are required by DEP to use less than 65 gallons per day per person.

This year's value is slightly lower than 2009's which is mainly due to a change in the way we calculate the population served.  We used to rely on prorating the Town Census results over the number of residential lots served by the public system compared to those that use private wells.  This year the population was calculated by taking the number of households served and multiplying it by the average number of people per household in Topsfield.

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.

Unaccounted for Water (UAW) is a commonly used statistic to gauge the health of water distribution systems.   It is the percentage of the annual withdrawal that is lost with no indication of where it went. There are times when UAW is a great measurement like when high percentages of water are lost.  A recent news story highlighted several communities that lost over half of the water they pumped.  The problems with UAW arise as conservation efforts become more successful, systems use less water and the systems age.

The main issue is that UAW is an indirect measure of a key piece of information that is readily available; in fact it is used in the calculation of UAW - the volume of lost water.  An example is a system that looses the same volume for two consecutive years but withdraws more water the second year than it did the first year. In this case the same volume is lost but the UAW declines which indicate an improvement that did not occur. Similarly if a system looses the same volume each year but withdrawals go down in the second year then UAW goes up even though less water was used.

The health of a water distribution system is commonly gauged by a statistic known as Unaccounted for Water (UAW).  It is normally expressed as a percentage of the total volume withdrawn during a given year. The volume lost is the difference between the volume withdrawn and the volume that is accounted for.

The easiest way to account for water is through billing.   All of the servcies in Topsfield are metered and we can quickly calculate the total volume of water billed in a year.  The  billing cycles for two-thirds of our customers do not match the calendar year but the differences occur in the winter time when water use is generally lower and more likely to be consistent from year to year. The Department of Environmental Protection allows us to also account for water use that can be 'confidently estimated'. Estimated use includes water used for fire fighting & training, hydrant flushing , water main breaks, drain cleaning and street sweeping.