Hello, I have a new cabin that will be used one weekend a month in the winter. (Minnesota) I will leave the propane heater set at about 40* or 45* when I am not there but it could fail so I want to protect my pipes etc. I'm planning to turn off the water from the well and use the curb stop to drain the system. My toilet will still have a little water in it. We picked up some RV antifreeze from WalMart yesterday. How much should go in the toilet? I assume it should go in the tank and in the bowl. If I do this 1-2 times per month will it hurt my septic system? Any other suggestions or hints would be appreciated.