TOTAL DISSOLVED SOLIDS 

According to Montana State University TDS is a measure of the material in a water sample that is smaller than 2 microns (2 millionths of a meter) and cannot be removed by a traditional filter. TDS is basically the sum of all minerals, metals, and salts dissolved in the water and is a good general indicator of water quality

Alkalinity, pH, and total dissolved solids (TDS) are three basic parameters which generally do not fluctuate dramatically in well water over time and can therefore provide valuable insight about the water supply.

When you have a salty or metallic taste in our water it could indicate toxic minerals are present.  It is likely that there are other harmful contaminants in the water.  Monitoring your TDS and pH is important. If they change than actions can be taken immediately.   The EPA recommends a maximum level of 500mg/L of TDS in your water

TDS can come from chlorine water treatment plants, pesticides and herbicides from agricultural runoff, and lead that may come from old plumbing pipes.

According to DRINING WATER AND HUMAN HEALTH The best option for dealing with elevated TDS depends on the specific ions present and their concentration. For example, if the elevated TDS is due to calcium and magnesium, a water softener is a good option. The process may not reduce the TDS concentration, but it will manage the aesthetic problems associated with the ions. If the problem is associated with an elevated concentration of nitrate, a reverse osmosis system or distillation unit can be used. The best option for dealing with TDS in drinking water should only be determined after analysis of the specific ions contributing to the TDS measurement.

• https://www.safewater.org/fact-sheets-1/2017/1/23/tds-and-ph
• https://drinking-water.extension.org/drinking-water-contaminant-high-total-dissolved-solids/