The glycol solution must be checked at least once a year in accordance with the manufacturer's recommendations. A base line analysis should be performed within two to four weeks of initial mixing. This measurement will be used to verify that the fill was completed properly, and will serve as a reference point for comparison with future test results. As a bare minimum, the solution should be analyzed for glycol concentration, solution pH and general fluid quality.
Concentration can be easily and accurately checked using a handheld refractometer. Most quality instruments will test glycol concentrations from 0 to 55% directly, are portable, and require no complicated adjustments for temperature. System concentration should not vary significantly from test to test. Progressively lower concentrations indicate a loss of glycol through a leaking joint or component. Find and repair the leak and add an appropriate amount of concentrate to return the system to its design concentration.
While high quality glycol solutions may last in excess of 20 years, hard use, improper maintenance or chemical contaminants will significantly shorten fluid life. Fluid pH serves as a good barometer for the condition of the glycol and is best measured with a field pH meter. This method is significantly more accurate than litmus paper tests.
Although glycol fluid pH is primarily a function of the corrosion inhibitor, and therefore, will vary from product to product, a few rules of thumb will be helpful in determining what constitutes proper pH. Most concentrated inhibited glycols have a pH in the 9.0 to 10.5 range. When diluted in a 30% to 50% solution, the pH falls to between 8.3 and 9.0. A pH reading below 8.0 indicates that a significant portion of the inhibitor has been depleted and that more inhibitor needs to be added. When the pH of the mixture falls below 7.0, most manufacturers recommend replacing the fluid. A pH value of less than seven indicates that oxidation of the glycol has occurred. The system should be drained and flushed before severe system damage occurs.