Can I use tap water / What kind of water should I use?
Yes, you can, but it is not ideal. Tap water contains many minerals and organic substances that may not taste very good in your coffee. Your water should have a mineral content of between 100 and 200 mg/l. Never use distilled water!
Never use distilled water!
Extraction is a chemical reaction, so you need minerals in your water to extract the flavours from the coffee. To find out what the mineral content of your water is, check out this website.
A water with a high mineral content that goes well with our coffee is Volvic.