It is safe to say that Grey Water is not contianing any Body Fluids could be dumped onto the ground. I prefere not to do this in a truck stop though.
Also watch in the winter time that if you hold any water get it emptied asap as it will freeze and crack your holding tank. Same goes for fresh water tank. Do not let that water freeze, I kept a close eye on the truck one night went over to to it when the low fell in the signle digits, truck temp dropped to 23 inside and than the sun came up 2 hours later and it did not freeze. If the inside temp would have stayed there for a few more hours it was gona freeze. As for the spicket you must shut off the pump and keep the faucet open or it will crack your spicket.
If your gona be away for more than a day and the temp is gona get low protect yourself and empty all Liquids for Preventive Maint.
I love my water source, brushing my teeth, washing my face, body parts, I do not understand how someone could live without it out at least not a sink. Mine did go down and it was a pain to buy one gallon jugs but at least I had a sink.
I did not realize at the time I had the Shore Power on my sleeper but in the future I can put a space heater in the truck and have it come on once an hour for five minutes and this will solve that problem just a suggestion.