Salary. The Bureau of Labor Statistics reports that marketing managers in the United States earned an average annual wage of $126,190 as of May 2011. The median wage, or midway point between the lowest and highest salary, was $116,010 per year.
What is TDS. TDS is the total of all dissolved solid matter such as minerals, metals, salts and. contaminants in the water. B. How TDS is Determined. TDS is most often determined in pool and spa water by using a conductivity meter. These. electronic meters measure the waters' ability to conduct an electric current.
Pool water problem - calcium hardness. Total hardness in swimming pools is a measure of all the dissolved minerals such as calcium, magnesium and sodium. For practical purposes we usually use calcium hardness as a reference in pool water chemistry. The recommended level for calcium hardness is 200 - 400 ppm, and both high and low levels result in swimming pool problems.