## 1 Introduction  
Water quality is a critical aspect of public health, environmental well-being, and sustainable development. Safe drinking water must be free from chemical, biological, and physical contaminants to ensure it is safe for consumption and use. Water quality directly impacts human health. Waterborne diseases, such as cholera and dysenterry, are prevalent in regions with inadequate sanitation and limited access to treated water. Ensuring clean water significantly reduces disease rates and improves the quality of life. Furthermore, good water quality is essential for agriculture and industry. In agriculture, irrigation with contaminated water can compromise food production, while in industry, water quality affects process efficiency and equipment longevity. Thus, water monitoring and treatment are essential priorities. In Portugal, public water systems serve 96% of the population, but this coverage falls to 80% in rural areas [1]. Despite this, many rural inhabitants use private water sourcesfor drinking and recreational activities. Thus, water laboratories are essential for owners to verify water quality. In addition to performing analyses, some labs offer to collect and transport water samples from wells, boreholes, and pools. In recent years, laboratories have sought to respond to economic, technological, and social challenges by adopting new organizational models and creative, innovative technological solutions to satisfy customers and become competitive against the competition [2]. Indeed, with increasing competition, customer satisfaction is a key factor in retaining and fostering client loyalty, as dissatisfied customers may not return [3]. Even without making complaints, dissatisfied customers can spread negative opinions and deter other potential clients [4]. Defining satisfaction is not an easy task, as it is a dynamic and subjective concept. According to [PERSON] et al. [5], customer satisfaction is defined as the evaluation of performance, which can be either positive or negative, depending on previous interactions with the organization. [PERSON] et al. [2] suggest that the level of satisfaction is related to perceived quality, with satisfaction being a function of perceptions and expectations. If perceptions fall short of expectations, the customer will be dissatisfied; if perceptions meet expectations, the customer will be satisfied; and if perceptions exceed expectations, the customer will be very satisfied. ISO/IEC 17025 standard plays a pivotal role in enhancing quality and customer satisfaction within testing and calibration laboratories. This adherence to quality management principles directly impacts the credibility of the laboratory's results, fostering trust and confidence among customers. The standard mandates rigorous procedures for method validation, equipment calibration, and staff competency, which collectively reduce errors and improve the consistency of outcomes. Moreover, the emphasis on impartiality and confidentiality protects customers' interests and data, further enhancing their trust in the laboratory's services. In essence, ISO/IEC 17025 helps laboratories to consistently meet or exceed customer expectations, thereby driving customer satisfaction and loyalty through a demonstrable commitment to quality and excellence [6]. In today's competitive landscape, understanding customer satisfaction is crucial for any business. For a water laboratory, this is particularly important as it reveals how well the laboratory meets customer needs and expectations. Analyzing feedback allows the laboratory to identify areas for improvement, enhance service quality, and ensure operational efficiency. This not only helps retain customers but also builds a strong reputation, fostering trust and credibility. Therefore, this research aims to assess customer satisfaction with the services provided by a water laboratory.