Is the CalChem okay to use on heating system with other additives?

We have not come across any issues when the product has been added to systems with other product is but the official answer is that you should always drain down any existing product, clean and then re-fill.

This is due to the fact that we would not know what is in the make-up of every product that may be in the industry and therefore is the reason why we would always recommend to drain, clean and re-fill.