Bring the water to a boil; set aside and let cool before using.
Wash the lemons with a vegetable brush and hot water to remove any reside of pesticides or wax; pat the lemons dry. Using a vegetable peeler, take all the lemon rind/zest off of the lemons. NOTE: Use only the outer part of the rind. The pith, the white part underneath the rind, is too bitter and would spoil your limoncello. Learn how to zest a lemon.
Place the rind/zest peelings in a large glass or ceramic container that is large enough to hold all the ingredients. Add the cooled water, sugar, and alcohol; stir to combine. Cover the container and set aside for 4 days (stirring occasionally, 1 to 2 times daily, for 3 days).
On the 4th day, taste the limoncello. If you think the taste is too strong, you can add additional water. NOTE: First boil the water and then let it cool. Then add the cooled water to the limoncello.
You are now ready to bottle. To bottle the limoncello, use sterilized bottles only. Strain the rind/zest from alcohol by placing some cheesecloth on a funnel to make sure that no rind/zest gets into the limoncello. Discard the lemon rind/zest.
Store your bottles of Limoncello in the refrigerator or freezer until ready to serve.
Makes enough for approximately 3 to 4 (750 ml) bottles.