Informal water providers play a critical role in addressing water supply gaps, especially where rapid urbanisation outpaces the expansion of water networks. They are widespread in Sub-Saharan Africa (SSA), where over 80% of workers are informally employed, and approximately 70% of the population lack access to improved drinking water. Amidst lags in progress towards SDG 6.1 of universal and equitable access to safe and affordable drinking water, there has been growing interest in the role of these vendors and how co-production between formal and informal water supply actors might improve outcomes for different types of consumers. However, we know little about the coordination mechanisms in place and how they operate in practice. We conduct a scoping review of empirical research over the last 20 years to develop insights regarding the different types of co-production that may increase water access. We reviewed published sources to develop a better understanding of the water sources and delivery methods of informal water vendors, and the mechanisms of coordination between formal and informal sectors. To supplement the findings, we develop illustrative examples of the evolution and dynamics of different coordination mechanisms. The article shows how formal (often public utilities) and informal (often private and small scale) water providers are co-producing service delivery in SSA, with insights regarding the different coordination mechanisms that might help or hinder efforts to increase water access. We find that enforcement capacity is crucial for effective coordination, which creates a dilemma: many regions most dependent on informal water providers are least capable of monitoring, let alone enforcing rules. Consumers can benefit from coordination mechanisms that require less effort, such as quality testing, technical assistance, and preferential rates for bulk resale. By specifying how the formal and informal sectors are linked, further studies on co-produced water systems can contribute to evidence regarding what coordinated service delivery options might offer short- and medium-term solutions.