Mount again the equipment which was eventually dismounted after the season end. Control the condition of the filter, conduits and electric installation. Pay special attention to any signs of rust or cracks. A swimming pool made of plastics will most probably have to be polished and waxed in order for it to get a new shine. It can be done in the same way as plastic boats are made ready for the season, using the same cleaning and polishing agents. If the swimming pool is very dirty, you can use gelcoat cleaner, a special product used for cleaning gelcoat surfaces.
Only the part of the swimming pool which is above the water surface should be polished. Water is supplied till it covers half the skimmer. Through the pump strainer basket, pump conduits should also be filled, to avoid pump dry operation. The pH value needs to be measured and stabilised and chlorine needs to be added.
NOTE. The drain pump should be running at all times and should be checked at least once a week.