Method of estimating total volume of an irregular wetwell

For use in a system which tracks liquid throughput at a wetwell for purposes of improving the pumping efficiency of the wetwell, the wetwell including pumping means and having:

• a) a geometrically regular upper portion defining, between an upper level sensor means and an intermediate level sensor means, a first volume which is easily calculated from its geometry, and
• b) a geometrically irregular lower portion defining, between said intermediate level sensor means and a lower level sensor means, a second volume which is not easily calculated from its geometry;
• a method of estimating said second volume, comprising:
• A) calculating the said first volume by multiplying the cross-sectional area of the upper portion by the vertical distance separating the intermediate level sensor means and the upper level sensor means;
• B) performing a series of cycles each consisting of allowing the wetwell to fill with liquid between the lower level sensor means and the upper level sensor means while the pumping means is off or is set at a consistent lower rate, then causing the wetwell to be emptied from the upper level sensor means down to the lower level sensor means by running the pumping means;
• C) during the filling part of each cycle, noting the time T.sub.2 required for the liquid to rise between the lower level sensor means and the intermediate level sensor means, and the time T.sub.1 required for the liquid to rise between the intermediate level sensor means and the upper level sensor means;
• D) for each cycle, multiplying the said first volume by the expression T.sub.2 /T.sub.1, this being the equivalent of dividing the first volume by T.sub.1 to get the inflow rate and then multiplying said rate by T.sub.2, thereby to arrive at an estimate of the second volume;
• E) storing each calculated estimate of the second volume;
• and
• F) averaging said estimates to provide a good approximation of the actual second volume.