Unless you know the actual system volume, it would be tough to partially fill with demineralized water and then pump in the appropriate amount of glycol. Buying full-strength glycol and mixing it at the jobsite using demineralized water from the Caleffi HYDROFILL is a great solution. Blend the glycol with HYDROFILL demineralized water to the proper percentage in a drum or directly in the tank of a fill/flush pump cart such as the Caleffi NA25510 HYDROFLUSH. Then fill the system with the blend.
Looking for more info? Check out our Coffee with Caleffi webinar Water Quality for Hydronic Systems archive to learn about the features and benefits of the HYDROFILL product.