If it's not aluminum you can use dishwasher detergent. Just put 1 pak, or about 2-3 tbls of powdered dishwasher detergent into the basket, fill the pot to the max fill line with cold water, run the pot thru a brewing cycle, unplug and let stand for about 30 mins. Pour out all the dirty water, and rinse thoroughly. It should now be spotless. This works everytime. But if you use this method in an aluminum pot it will turn the pot and basket black. You will then have to repeat the same process, but then using Cream of Tartar instead. The Cream of Tartar is acidic and will remove the bloack caused the alkaline of the dishwasher detergent.
HTH.
Eddie