TDS stands for "Total Dissolved Solids," and it represents the amount of "stuff" that is dissolved in a liquid. This stuff, for our purposes, is typically minerals, but it can also be organic matter, or even some chemicals (depending on where your water is coming from).

Why Does TDS Matter?

TDS matters because it effects the level of extraction you can get out of your coffee. Coffee requires minerals in the water you brew with so you can pull the desired flavor out of the grounds. Empty water (water with a TDS of 0) will leave your coffee tasting dull and flat because it doesn't have any of the required solids to extract the flavor from your coffee.

The SCA (Specialty Coffee Association) created a water standard that acts as a guide for your coffee brewing water. The recommended TDS is a target of 150 with an acceptable range of 75-250 TDS.

TDS will not tell you the exact amount of individual minerals are in your water, just the total amount, hence total dissolved solids. This helps provide a benchmark to help you dial in the right minerals. If you want to know which minerals are in your water and at what concentrations, you'll need specific tools like a photometer or titration kit to measure certain minerals.

Mineral Quantity and Quality

The proper amount of minerals is not the only thing you want to be wary about, however. You should also look at the kind of minerals for your brewing water. Certain minerals can cause limescale to build up in your brewer or kettle, as well as corrode and damage the boiler in your espresso machine.

All of Third Wave Water's mineral profiles utilize what is known as "permanent hardness" to protect your equipment from limescale buildup. TWW's Espresso Profile lacks chlorides, which can be harmful for your espresso machine. More on permanent hardness and machine health later ;)