Purpose This research aims to study a broad range of sustainability aspects and develop a set of indicators with their subjective relevance to each of the sustainability dimensions that will help to improve the sustainability level of the water system of Nur-Sultan (Kazakhstan). Design/methodology/approach The broader list of indicators (which were identified through a thorough review of the literature) was assessed by water-related industry professionals and experts who were asked to assess the compliance of suggested indicators to five criteria of sustainability using a Likert scale. Findings It was found that the highest-ranked indicators across all five categories were mainly related to the chemical and physical quality of water, followed by availability of individual water meters as well as water supply tariffs' adjustment to users' income, and issues of ageing infrastructure. The lowest-ranked indicators among all categories were mainly related to investments into research and development, water management and awareness, feedback systems and flexibility. The least ranked indicators are seen to be more related to the scenarios when basic needs are covered and the stakeholders have extra time and resources for advancing the levels of water infrastructure sustainability. Practical implications The ranked and categorized indicators can be used as a powerful decision-making tool to improve the sustainability of the water system of Nur-Sultan or any other city in a developing country. Originality/value By conducting this study, it was aimed to address the aforementioned gap in the field in terms of running a wider scope assessment of indicators rather than looking at conventional environmental and socio-economic aspects. This provides novelty to the study, especially in the context of developing countries that need more guidance in terms of sustainable development of the water-related infrastructure.