The International Association of Plumbing and Mechanical Officials (IAPMO) is excited to announce that the Water Demand Calculator version 2.0 — with new and enhanced features — is now available for download.

While the basic template of the calculator remains intact, several new features have been added along the edge. The most significant new feature is the addition of a drop-down menu that offers a selection between a single- and multifamily building. The multifamily option activates two additional input boxes that require the user to specify the total number of apartments that are (a) in the building and (b) in the calculation. The latter entry is dynamically linked to the probability of fixture use column in the calculator, gradually reducing the percentage as the number of apartments increase. This new calibrated feature assures accurate predictions of peak water demand in large multi-family dwellings.

Another feature of WDC version 2.0 is the display of additional computed information pertaining to the peak conditions. Besides providing the total fixture count and the 99th percentile demand flow, WDC version 2.0 gives the average number of simultaneous busy fixtures in use at any instant during the peak period (called the Hunter Number) and the probability of no flow (stagnation). A download button is provided for users who wish to save computed results in a notepad.

“The Water Demand Calculator has become more robust while remaining fast and user friendly,” said Dan Cole, IAPMO’s senior director of technical services. “Increasing the accuracy in predicting peak water demand for multifamily dwellings will lead to reductions in pipe sizing accompanied by increased cost savings.”

The Water Demand Calculator version 2.0 may be downloaded at www.iapmo.org/water-demand-calculator. For specific information about the Water Demand Calculator or to provide feedback from using it, please contact Dan Cole at dan.cole@iapmo.org.