A 50/50 mixture by volume of distilled water and ethylene glycol, pre-filtered by a 10 micron filter. During filling of the system or servicing, it is essential that no contaminants enter the system. For this reason filtering of the fluid as it is poured into the system is recommended. This can be achieved by using filter
paper in a funnel. If filter paper is not available, coffee
filters are an alternative but first test their stability with
the glycol solution. Not all ethylene glycol solutions are
the same, some additives, especially silicone additives,
are thicker in consistency and will clog the critical
components in the system.
