We used the Delphi method to identify areas of consensus and disagreement in managing building water systems. One hundred and six experts were invited, 25 of whom completed both rounds. More than 95% of experts agreed that current plumbing codes are not adequate and return loop temperature should be monitored. A notably low percentage of experts agreed on the required level of chloramine (i.e., 32%) and flushing frequency (22%), despite these being common control strategies. Consensus was not achieved for temperature and disinfectant residuals, but a plurality of respondents indicated that a temperature of 55°C was appropriate and that low but detectable levels of disinfectant residuals are appropriate. After Round 2, a majority of the experts agreed that the knowledge syntheses provided were helpful and unbiased. Findings from this study will help stakeholders by providing helpful insights on plumbing code, design factors, operational factors, and water quality monitoring practices.