<p style="margin: 0px;">About antifreeze, I found this answer by googling ... He says</p><p style="margin: 0px;"> </p><p style="margin: 0px;">"If I may, as a chemist, weigh in here on this issue, I'd like to say that RV antifreeze, the non-toxic stuff, contains propylene glycol, which is also used in foods and cosmetics. It is the only antifreeze you should use in your RV water system, gray water or black water tank, toilet, or traps. Using regular automotive antifreeze, which contains ethylene glycol is a really bad idea because it is not biodegradable and is highly toxic. Windshield washer fluid is a really bad idea too, because not only is it toxic it is highly volatile and explosively flammable. The vapors can kill you, either by poisoning you or by catching fire and/or exploding.<br><br>I've bought both RV antifreeze and automotive antifreeze within the last month, and the RV antifreeze was less than half the cost of the automotive antifreeze, and although both were more expensive than the windshield washer solution, I'd still go with the RV stuff for these applications.<br><br>The auto antifreeze is bad news in a septic tank and illegal to dump down a sewer, and for good reason. Windshield washer solution will also dry out fairly quickly, certainly quickly enough to be of no use over a winter.<br><br>And although the RV stuff recommends you not dilute it, doing so to the tune of say 50/50 with urine or even water will certainly raise the freezing point, it will probably not do so enough to cause a problem at the temperatures at which people might be tempted to go camping.<br><br>Oh, and for what it is worth, both antifreeze solutions make fine coolants. But please use the correct one. Your car, your RV, your spouse, your kids, and the environment all thank you. " <br></p><p style="margin: 0px;"> </p><p style="margin: 0px;"> </p>