You can make your own descaling solution by using vinegar and baking soda.
You can also use a mixture of equal parts of white vinegar and water to make your own descaling solution.
Other ways to make your own descaling solution are to use some citric acid or lemon juice, although the citric acid or lemon juice may require more frequent descaling cycles to fully descale your coffee pot or Keurig or other machine.
If using vinegar and water as a descaling solution, simply mix together equal parts of white vinegar and equal parts of water in a container.
Then pour the solution into your Keurig or coffee machine and start the brewing process.
If using lemon juice, simply use a 1:1 mixture of water and lemon juice and pour the solution into the Keurig or other coffee machine to descale and run it through a brew cycle.
If using citric acid you can dissolve a teaspoon of citric acid powder in 2 quarts of water and then pour the solution into the Keurig or coffee machine and run it through a brew cycle.
If using baking soda, dissolve 1/4 cup of baking soda in 1 liter of water and then pour the solution into the Keurig or coffee machine and run it through a brew cycle or descale cycle depending on your machine.
For heavy scale buildup you may need to use some commercial descaling solutions but for most descaling a homemade descaling solution will often work just fine.
Also be sure to rinse the machine thoroughly with water and run straight water through a descale cycle or brew cycle to remove any of the baking soda, vinegar, citric acid or other descale solution.