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www.fueloilnews.com | FUEL OIL NEWS | FEBRUARY 2014 39 Water Quality Though often taken for granted, the quality of water mixed with glycol con- centrate can have an enormous impact on system performance. Marginal qual- ity water can lead to the development of scale, sediment deposits or the creation of a sludge in the heat exchanger which will reduce heat transfer efficiency. Poor quality water can damage the system by depleting the corrosion inhibitor and pro- moting a number of corrosions including general and acidic attack corrosion. Since it is vital to use high quality water for glycol dilution in order to maintain sys- tem efficiency and prolong fluid life, you must ensure your water is of sufficiently high quality. Good quality water contains: • Less than 50 ppm of calcium • Less than 50 ppm of magnesium • Less than 100 ppm (5 grains) of total hardness • Less than 25 ppm of chloride • Less than 25 ppm of sulfate Check with your county or city water department to determine the chemi- cal properties of the local water. If your mixing water will be drawn from a well, which typically has extremely hard water, or the local water authority cannot pro- vide an accurate profile we recommend either testing the water yourself or hiring a commercial water treatment specialist to analyze the water. A simple test used by Dow Chemical Company to ensure that water contains less than 100 ppm of hardness, is to fill a small sample bottle with 50% glycol and 50% water. Let the solution stand for 8-12 hours, shaking it occasionally. If any whitish sediment forms, the water is too hard and should not be used to dilute the glycol. In those cases where tap water does not meet the standards for quality, Dow recom- mends using demineralized water that has been distilled, deionized or passed through a reverse osmosis process to remove harm- ful minerals and salts. A suitable corrosion inhibitor must be used with demineralized water since the pH of the treated water may be measurably less than seven. Fluid Maintenance The anti-freeze 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 com- parison with future test results. As a bare minimum, the solution should be analyzed for glycol concentration, solution pH and general fluid quality. concentration testing 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 sig- nificantly from test to test. Progressively lower concentrations indicate a loss of gly- col through a leaking joint or component. Find and repair the leak and add an appro- priate amount of concentrate to return the system to its design concentration. solution pH testing While high-quality glycol solutions may last in excess of 20 years, hard use, improper maintenance or chemical con- taminants 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 prod- uct, 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 replac- ing 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. For additional product specific information, contact the applicable chem- ical manufacturer. systeM FlusHing Should the system require cleansing after removing old or damaged anti- freeze, flush the system with a heated 1%-2% solution of trisodium phosphate for 2 to 4 hours, then drain and rinse thoroughly. Flushing the system prior to the initial introduction of the glycol solu- tion is also highly recommended in order to remove excess pipe dope, cutting oils and solder flux. HVAC/ HydroniCs By Larry ashton, P.E., rayPak Table 1. Freezing Point