I only use RV anti freeze from a sealed jug - and some is often a year or so old. If I have any left after a winterizing, it ends up dumped in the bottom of the waste holding tanks via a drain just to get rid of it.
As far as a drain trap on an RV, a lot of them use a HEPvO (
https://hepvo.com/) instead of a conventional 'P' or 'S' trap, mostly for space saving. This means that whatever anti freeze you put down the drain, it ends up in a waste water tank.
Opinion - if you are using more then a 2-3 gallons to winterize an RV, it sounds like you may be winterizing the HW heater which can probably be bypassed after draining and left empty.
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