Institutions are the rules of the game that guide policy behavior. Yet, the policy and administration literature on institutions and institutional design have been developed largely in parallel to policy behavior and network literatures. Drawing insights from both, we apply the Institutional Grammar Tool along with survey data to assess how addressing collective action problems result in variations in institutional designs and how rules influence behavior. Our case is the New York City Watersheds, where New York City, local governments, the State, and the Federal government agreed to secure access to high‐quality, unfiltered drinking water for New York City. Despite a long history of conflict, the parties devised a complex governing arrangement that created credible commitments while providing for a variety of public goods. Results show that rule configurations differ depending on whether they create credible commitments or provide public goods, and that credible commitment rules guide collaboration patterns among stakeholders.