¡Look at (and READ) the pink stuff jug!
On the advice of a friend that used to be a product engineer for a major OE chemical supplier, I have started reading the jugs of RV anti-freeze that I have. The old ones were straight Propylene ...
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I looked at a bottle of PEAK and it has ethyl alcohol and a bunch of other junk and dye. The most important part said GRAS (generally regarded as safe.) I used to just blow the lines out but somehow water pooled and froze. now I blow it out and add pink. It washes out and you should sanitize anyway.
