The success or failure of most medium and large plants in the region not only depends on efficient design, construction quality etc, but considerably depends on their operation and maintenance. Though most RO plants have state of art equipment and employ latest technology they lag behind substantially in specific areas of hands-on experience of their operation personnel due to which certain critical aspects get neglected and overlooked. This vital area inspite of being critically important, is probably the least appreciated. It is this most critical aspect which probably forms the weakest link in the chain and in most cases negatively impacts the RO plants in the Middle Eastern region. This paper attempts to outline several of such important O&M factors based on practical result oriented experience and underlines the benefits such experience contributes to the RO plants performance, availability and consequently to its total water cost.