Take a wide pan and add mango pulp and raw mango pieces.
Also add sugar, citric acid and out of 5.5 litres, add 2 litres of water.
Note : Citric acid works as a preservative in this recipe. If you don't have citric acid, you can add 1/2 tsp of vinegar or lemon juice once the frooti is completely ready.
Cook for 20 minutes or until mangoes turn soft and mushy.
Remove from the heat and let it cool completely.
Note : If you have hand blender, then you can immediately blend the mixture even while it is extremely hot but in case you don't have it, then you have to wait for the mixture to cool completely before putting in grinder jar.
Once cool, put the mixture in grinder jar and grind to a smooth puree. As the grinder is small, then you have to do this process in batches.
Pass the grinded mixture through a fine masher and collect the puree in a bowl.
Now add rest of the 3.5 litre drinking water and mix well. However amount of water can be adjusted as per the required consistency of frooti.
Note : At this stage you must taste your frooti and if you find the sweetness is not enough, you can add powdered sugar now.
Cool completely before serving.