Abstract: Some embodiments provide a pool filtration system for filtering pool water including a pump, a primary filter in fluid communication with the pump, and an auxiliary filter in fluid communication with the pump and the primary filter. The auxiliary filter can include a membrane filtration module, and a flow distribution manifold. The flow distribution manifold can include an influent port in fluid communication with an influent flow opening and an effluent port in fluid communication with an effluent flow opening. The influent flow opening and the effluent flow opening can be fluidly coupled across the membrane filtration module. The flow distribution manifold can further include a bypass mechanism. The bypass mechanism can include at least one valve that selectively fluidly couples the influent port to the effluent port to bypass the membrane filtration module.