If your system has a propylene or ethylene glycol fluid in it. We recommend first looking into this troubleshooting guide as this is more likely related to the cause of your pH change.
A chemical addition to the system could result in either an increase or a decrease in pH within the system.
Any treatment addition logs for chemical addition that may have occurred between your last test and this one
Contact facility operators to see if there was any known chemical addition since your previous test
Sometimes unknowingly, for example, if a chiller had maintenance and the mechanical company performed an acid cleaning on the tube bundle, but failed to drain and rinse the chiller properly. This scenario could lead to a change in pH of the broader system.
Closed loop systems should be “tight” and not lose water at much more than a rate of 1-5% of their total volume per year. Some of this loss is due to recurring maintenance tasks that require draining system water. When the system loses water, more water than is needed to bring the system pressures back to normal will need to be treated. This is referred to as a makeup water dilution – the result of system water loss.
It is common for non-glycol closed loops to have a pressure reducing valve (PRV) between the system and the makeup source, providing an automated fill when the system pressure drops below the PRV setting. Other systems may still require operators to manually open a fill valve to add water when low pressures on the system begin to occur.
Meters may be improperly installed, improperly sized (especially on low flow activation thresholds), or old and no longer functioning. All of which may cause them to register flow volumes, typically resulting in under-registration.
If you have determined water loss is likely the cause, finding a solution may not be so easy. System leaks are not always apparent and may require specialized leak detection services or methods to determine the source.
Microbial fouling is another source of pH change in the close loop systems. Unlike cooling towers, most of what is produced in the closed loop stays in the water until someone does something about it. Metabolic products from microbial activity can cause fluctuations in the pH both up or down.
Total Aerobic Dip-slides – Less likely, but not impossible, in closed loops as they are non-aerated systems.
ATP levels – Fairly good general measure of microbial activity in systems
Anaerobic microbes – More likely to be source of fouling in closed loop systems (IRB, SRB, and more)
Check with this troubleshooting guide to go more in-depth with microbial fouling in closed loop systems.
By this point if you still have not found out what the source of your pH change is, then there could be some more site specific causes like process water contamination. Now would be a good time to approach your manager to discuss the situation and determine how to proceed within your company's guidelines.
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Max M.
MHWTec - Denver, CO
Produced in affiliation with Association of Water Technologies