A water treatment apparatus includes a frame and a plurality of connecting accessories, manifolds and filter cartridges. Each of the connecting accessories includes a seat ring fixed on the frame and a communicating pipe coaxially received in the seat ring. The seat rings together with the communicating pipes are spaced at a distance from one another. Each of the manifolds is suspended between adjacent two of the connecting accessories and has inlet and outlet ports at opposite ends. The inlet and outlet ports of each of the manifolds are rotatably and coaxially received in adjacent the seat rings respectively with their exterior walls in contact with inner walls of adjacent the seat rings and their interior walls in contact with outer walls of adjacent the communicating pipes. Additionally, the filter cartridges are detachably joined to the manifolds respectively.