Residential water demand modelling and hydraulic reliability in design of building water supply systems: a review

Abstract

The building water supply system is a fundamental unit in water supply systems as it is directly associated with end users. However, the studies available on its efficient design are limited. Water demand estimation continues to be an important issue in water supply systems' design because of its multifaceted nature. Hunter's curve, or Fixture Unit method, is widely used for estimating the load on plumbing. Regardless of its popularity, it has a few drawbacks and is arbitrarily modified in some plumbing codes. Fixture-use probability, a basic entity in the Fixture Unit and some other methods, is a difficult parameter to estimate. Commonly, high-resolution field data is used for stochastic modelling of residential water demand which may not be always available. The paper reviews important residential water demand models in view of their applicability in building water supply system design. The irregular nature of water demand in buildings is due to uncertainty in water-use behaviour of users at fixture level. Use of soft-computing techniques can provide an advantage over the other methods in modelling such behaviour. The paper also discusses reliability of building water supply systems and applicability of some common indices for estimating reliability of building water supply systems. HIGHLIGHTS Mostly, residential water demand models use high-resolution field data.; Fixture use probability is obscure and difficult to estimate.; Estimation of hydraulic reliability of building water supply systems is required.; Accurate estimation of water demand is neither possible nor required in the design.; Estimation of water demand and hydraulic reliability are interdependent but complimentary aspects for efficient design.;

Keywords

• building water supply system
• hunter's curve
• hydraulic reliability
• pipe sizing
• plumbing
• residential water demand