For grain brewing, we need some means of rinsing out the sugars retained by the grains after mashing. This is done by allowing water to pass through the grains to dissolve the remaining sugar.
For 'fly' or continuous sparging, I recommend a rotating sparge arm such as Phil's sparger (see pic). These are difficult to get hold of now, but many people have made DIY versions. Try searching the forum for more information.
Hot water at about 78C is fed into the tube at the top and passes to the sparge arm. This arm is drilled with small holes in such a way as to cause the arm to rotate with the force of the water coming out. This means that the water is evenly distributed over the grain bed automatically.
There is an alternative to fly sparging, known as 'Batch Sparging' which involves adding water in bulk to the grains rather than trickling it over. For more details, see /extras/brewing tips/.
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