RV antifreeze doesn't work like radiator antifreeze.. The pink stuff will freeze, or at least turn to slush. What it WON'T do is expand when it does freeze. It is intended to replace water in lines/tanks, not lower the freezing point of water. Diluting it 50/50, or any such combination, will not work. The water will still freeze and expand - that's where the damage to plumbing comes from. You can use it to flush your toilet by pouring some in after use. Holding tank will still solidify, but shouldn't burst. Get the propylene glycol stuff, NOT the less-expensive, alcohol-based (read: FLAMMABLE) variety. Last thing you want is a waste tank filled with flammable liquid! ST