Interesting read. From the conventional wisdom espoused around the web, I assumed that it was actually some kind of EPA ban on EG in raw water systems (due to it inevitably ending up going overboard). Is that the case? Anyone know if there's a MD state law regarding it?
One notable point mentioned in the blog is that antifreezes sold primarily for engine cooling systems contain additional additives for things like corrosion protection. I imagine the chemicals vary from one manufacturer to another. Would that not be a reason to prefer RV type PG in winterizing a raw water cooled engine?
Discharging either would be technically illlegal, but some is unavoidable. Most airplanes are de-iced with PG, but there is still some EG out there. The "reportable quantity" for spills of EG is quite large--several tons, I believe. Those that do restrict discharge specifically, generally treat EG and PG the same.
Certainly the largest discharge of EG and PG to the Chesapeake is BWI airport. There is some discussion here that should put a 1-gallon discharge into perspective.
http://www.marylandaviation.com/_me...vironmentaldocs/New_Horizons_BWI_Overview.pdf
As always, recycle what you can. But note that EG and PG are treated in a similar manner.
The corrosion inhibitors these days are generally 1-2 percent of an organic acid, something like benzoic or azaelic acid, some salts, and ppm levels of a thiazole coumpound. I'm not certain what is in the RV antifreeze, but I'm guessing there are some corrosion inhibitors, since raw glycols are a bit corrosive.
The Chesapeake Bay Foundation says "When you recycle, be sure you don't mix propylene glycol and ethylene glycol types of antifreeze", which is just plain false, as the recycler that serves the MES (government drop-off sites) mixs them together and is glad to have both. Good luck finding a waste PG tank; doesn't exist and there is no need.
