If you're buying your own minerals to improve your coffee, it might help to have your own TDS meter! TDS stands for Total Dissolvable Solids, the amount of minerals or aggregates found in the water chemistry. Some uses include:

• Verify the water you are adding
• Test your current water to see how many minerals are present.
• The cap can also be used to hold water to measure. Simply fill cap then insert meter and use as normal.
• NOTE: this will not define which minerals are present in your water, only that something is there.