One more thing about RV antifreeze,although they say it is non-toxic,I would never poor it into my water tank...Disconnect the line that goes to your water tank at the water pump and ad a short line that will reach your 1 gallon antifreeze bottle and suck the antifreeze right out of the jug instead of your water tank.
If you use antifreeze in your lines for the winter,flush/flush/flush in the spring.That stuff is nasty,safe or not,that's why I use air instead.
Rock salt works in the holding tanks also if your still using it in low temps.
Jayco
