I am planning a Sweet Potato Ale and was toying with the idea of using maple syrup or sap. One thought was to substitute a gallon of water with a gallon of sap, if that is economically feasible. I did read people saying to either boil with syrup or rack with syrup. What do you think?
You can either add maple syrup to the mash / boil, or add it in lieu of priming sugar for a subtler taste.
This link has information on brewing a bock beer with maple syrup.
Well it depends on what you want out of the brew. If you want some maple syrup flavor in the final brew, using syrup is the way to go. Adding it late in the boil with preserve some of the aromatics. It is nearly 100% fermentable, so using it for priming is probably the best idea to really preserve flavors.
Sap tastes like a strange water. If you boil 6 gallons down to 5 gallons it tastes like...strange water. You need to boil it down considerably for it to taste even remotely maple-like. Using sap is a novelty thing, but it does nothing for the flavor of the brew really. And using one gallon of sap will really taste like nothing was added.