Don't Understand Value Of 3-Valve Hot Water Bypass

I've blown out the lines and still have had water in low spots, so that is why I bypass the water heater. Instead of RV antifreeze, I pour cheap vodka in, run that through the lines, then blow all that out with the air compressor. The alcohol inhibits mold growth, and any water that is in low parts will have enough booze in it so it doesn't freeze at 32 degrees.