During the past few years, there have been increasing trend on building appropriate model for supplier selection and a good supplier, indeed, is capable of providing better quality products, which could lead to increase the productivity of an organization. In this paper, we present an empirical investigation to find the effect of monitoring three different standards, namely, domestic, national and international standard on improving the quality of products in water and sewage projects. The proposed model of this paper designs a questionnaire and distributes it among some experts in a rural Water & Sewage firm located in city of Ahvaz, Iran. Using the Pearson correlation ratio, the study examines three hypotheses of the survey and the results indicate that there were poor relationship between carefully considering domestic, national and international standards and improvement on quality of products offered by various suppliers. In addition, job experience and type of employment also do not seem to have any meaningful effect on quality assessment of suppliers.