What is your objection to alcohol based other than alcohol in a non pressurized system can evaporate and leave you unprotected (Takes time however)
Suggestion The Best RV antifreeze I've ever used is air. Yup Air. I hooked up the old huffer puffer (Actually I sould not say that as that's an actual brand and I used a Crafstman) set the regulator to about 50 PSI and used a blow out adapter. Opened every valve and blew out the lines.. Then cycled the Ice maker manually to drain that line, Flushed toilets to drain those lines and blew again, and blew again.. Eventually I was getting no more water (About 10 blows) and then I put pink stuff in the drains and toilets I had an at-home sewer connection so I dumped and then added a bit more pink to protect the dump vlves With two toilets. 3 laves and a sink I used about 2 gallons of pink.
Next spring... Instead of having to get all that nasty pink out of the fresh water system..... Well let's just say that was NOT a problem... and as for the pink in the drains. not a problem either.
