A TDS meter is one of those simple but useful items to keep on hand. They allow you to test your water quality when waterfed window cleaning. Test your water for "Total Dissolved Solids" which are basically impurities and minerals in the water. They measure in ppm which stands for "parts per million". 100% pure water will give you a reading of 000 ppm. So the higher the TDS rating of water, the higher the amount of inorganic solids that are dissolved in the water. Always have an extra TDS meter in your work truck or office! Be sure to shop our full selection of Water Fed Accessories for other items you may need to complete your waterfed setup. You can also learn more about Total Dissolved Solids and how it impacts your purification system on our TDS page.