Well you could construct a gravity fed sand filter. This is a really old system that consisted a big concrete tank filed with sand. usually these are below the pool water level (underground) and the skimmer water just flows into the tank via gravity. It then trickles down through the sand and at the bottom there are lateral pipes to pick up the water and a pump returns it to the pool.
I have a really old pool (60ys+) that used to have this kind of system. There were so many pipes and valves you would have had to have a engineering degree to operate it! Its no longer functional but the underground room under the deck made a great location for my modern equipment.