What Are
Total Dissolved Solids?
Total Dissolved Solids are the total weight of all solids that are
dissolved in a given volume of water, expressed in units of mg per unit
volume of water (mg/L), also referred to as parts per million (PPM).
1. "Dissolved solids" refer to any minerals, salts, metals, cations or
anions dissolved in water. This includes anything present in water other
than the pure water (H20) molecule and suspended solids. (Suspended solids
are any particles/substances that are neither dissolved nor settled in the
water, such as wood pulp.)
2. In general, the total dissolved solids concentration is the sum of the
cations (positively charged) and anions (negatively charged) ions in the
water.
3. Parts per Million (ppm) is the weight-to-weight ratio of any ion to
water.
4. Conductivity is usually about 100 times the total cations or anions
expressed as equivalents. Total dissolved solids (TDS) in ppm usually ranges
from 0.5 to 1.0 times the electrical conductivity.
Where do
Dissolved Solids come from?
1. Some dissolved solids come from organic sources such as leaves, silt,
plankton, and industrial waste and sewage. Other sources come from runoff
from urban areas, road salts used on street during the winter, and
fertilizers and pesticides used on lawns and farms.
2. Dissolved solids also come from inorganic materials such as rocks and
air that may contain calcium bicarbonate, nitrogen, iron phosphorous,
sulfur, and other minerals. Many of these materials form salts, which are
compounds that contain both a metal and a nonmetal. Salts usually dissolve
in water forming ions. Ions are particles that have a positive or negative
charge.
3. Water may also pick up metals such as lead or copper as they travel
through pipes used to distribute water to consumers.
Why Should You Measure the TDS level
in your Water?
The EPA Secondary Regulations advise a maximum contamination level(MCL)
of 500mg/liter (500 parts per million (ppm)) for TDS. Numerous water
supplies exceed this level. When TDS levels exceed 1000mg/L it is generally
considered unfit for human consumption. A high level of TDS is an indicator
of potential concerns, and warrants further investigation. Most often, high
levels of TDS are caused by the presence of potassium, chlorides and sodium.
These ions have little or no short-term effects, but toxic ions (lead
arsenic, cadmium, nitrate and others) may also be dissolved in the water.
The following are reasons why it is helpful to constantly test for TDS:
