Authors: Omaghomi, T., Buchberger, S.G.

Variation in Peak Water Demand with Building Size: Parameters and Methods

Introduction

Variation in peak water demand with building size: parameters and methods. Learn how building size impacts peak water demand in homes with high-efficiency fixtures. This study refines estimation methods, offering a WDC based on fixture count, probability, and flow rate.

Abstract

Over time, water use in buildings has reduced due to low flow high-efficiency fixtures. The Hunter’s fixture units method of estimating peak water demand overestimates peak water demand especially for small buildings with efficient fixtures. Updating current methods of estimating demand requires the necessary parameters for efficient fixtures. High-resolution water used data collected at over 1000 single family homes in the US were analyzed to estimate peak hour probability values for high-efficiency fixtures. Results show that the size of the building affects the peak hour probability of a busy fixture. Furthermore, as building size increases and the number of fixtures increases, the water demand pattern transitions from discrete intermittent pulses to continuous random flows. The location of a building along the continuum between discrete and continuous peak water demand determines the applicable fixture probability values and the appropriate method for estimating peak water demand. To facilitate the use of an appropriate method for estimating peak water demand, a water demand calculator (WDC) was developed in Microsoft Excel. The WDC selects an appropriate estimation method based on the combination of three key parameters: n-fixture count, p-fixture probability of use, and q-fixture flow rate. Results from the WDC address conditions the current method (Hunter’s Curve) does not accommodate including the zero-demand dilemma and peak flow estimates for single fixtures. The WDC also reflects the effect of reduced fixture flow rate on the overall peak water demand and the required size of the premise plumbing.

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