The three different types of antifreeze that are most common are propylene glycol, ethylene glycol, and methanol. The first of which I have found to be the most popular, but any of these may be in your pipes and each have different methods for handling and their affects on system performance also vary. In design, our job as commissioning authorities is to assure that the owner understands the type of antifreeze that they are getting and that it is acceptable. We also check to make sure that the percentage is consistently the same throughout the contract documents and that the engineer's specifications spell out how the antifreeze is to be added to the system and whether regular drinking water is clean enough to add to the solution. This is important because of the changes in capacity of the heat transfer equipment and pumps can be lower depending on this percentage of the antifreeze and the quality of the water. We have had projects where the system required pre-mixed solution of glycol and filtered water because of the low water quality available at the site. Having this method spelled out is also important because of the various ways contractors add liquids to a system. What worked for them on the last couple jobs may be the wrong approach for this one. A mistake by a contractor at this stage, when filling the system can be expense because of the large volumes that are typically involved. Not to mention where the wrong solution mix would go? Down the drain? I would hope not!
In multi-facility groups, it would be in the owner's best interest to keep the type and percentage of antifreeze consistent. This is because the owner would then be able to write a common policy and procedure around handling the solutions, how they're added, how the percentage is tested and what procedure to follow when there is a spill. That way if the owner had to rearrange staff there wouldn't be any confusion or additional training required. At ECO Commissions we have helped many owners navigate these issues and establish policies that will help them for years to come.
Don't let what's in your pipes surprise you.