There are two common ways to measure the amount of total dissolved solids in a sample of water. The first method requires an extremely sensitive balance that can measure to the nearest .0001 gram. A 100mL sample of water is carefully collected from the middle of a stream. A 300mL beaker is carefully weighed. The water sample is poured into the beaker and allowed to evaporate in an oven at 103^oC. Allow the beaker to cool to room temperature before weighing. The beaker is then weighed again. Be careful not to touch the beaker with your hand as the oils and moisture on your hand will add weight to the beaker. The first weight is subtracted from the second weight and multiplied by 10,000 to determine the mg/L of total dissolved solids in the sample.

Another, simpler method requires the use of a Hach Pocket Pal TDS meter. This meter works by measuring the electrical conductivity of the water. Conductivity increases as the amounts of salts and other dissolved solids increase in the water. Conductivity and TDS are two different but related tests. One can be calculated from the other by multiplying or dividing by a certain fixed number. Pocket Pal TDS meters give an approximate result +10%.

Listed below are the directions for how to use a Pocket Pal TDS meter.

1. Remove the black, plastic, protective cap from the TDS meter.

2. Slide the ON/OFF switch (black button on top) to ON.

3. Lower the end of the TDS meter about 1 inch into the sample to be tested. Hold the meter straight up and down.

4. Gently swirl the sample for several seconds. After swirling, wait for the digital display to stabilize. Read the TDS value displayed.

5. Multiply the TDS value displayed by ten (10). Record results as mg/L.

6. Rinse the bottom of the meter. Replace the black, protective cap. SLIDE THE ON/OFF SWITCH TO OFF. Return the meter to where it belongs.