There are two descaling agents that you can use to make a DIY descaling solution. These are vinegar and citric acid.
To make a vinegar descaling solution, simply mix equal parts of vinegar and water.
The downside of the vinegar descaling solution is that it takes so long to rinse out of the coffee maker. If not done well, you can have a vinegar taste and smell in your brew.
The citric acid solution takes much less time to rinse out since it is odorless. To make, mix 1.5 to 2 tablespoons of citric acid with one liter of warm water. Stir to completely dissolve the citric powder.
Typically, it takes just 2 brewing cycles of fresh water to completely rinse out the citric solution. And, your next brew after descaling will taste great.