Do I need to drain black tank?

[Philip Jones]

Hi all,

We are currently in Florida and are returning home to Canada tomorrow. Temperatures at home will be down to -7 C at night and going up to 2-6 C during the day, at least for the next week. After the next week, we expect above freezing temperatures and will be out of the “danger zone”.

During our travel home we will be staying at Walmarts for two nights. It will be very inconvenient for us to go into the store just to use the toilet.

If I winterize the pipes with compressed air before we leave Florida, is it safe to continue to flush the toilet with bottled water en route and leave some (< 40% of the tank) liquids in the black and grey tanks during the freezing temperatures? I would think that the tank contents would have plenty of room to expand upwards without rupturing the tank, but I don’t know if this is true.

Many thanks for any advice,

Phil

[Adventure.AS]

In freezing weather or when travelling for mileage, we use disposable waste bags. They can be found at Walmart. Saves the hassle of emptying the black tank at the destination.

[Mollysdad]

Originally Posted by Philip Jones

I would think that the tank contents would have plenty of room to expand upwards without rupturing the tank, but I don’t know if this is true.

Water ice is a unique compound. Most materials shrink as they get colder, and so does water, but at a certain point it starts to expand (4 C.). That's why you can't freeze liquids in glass. The bad news is it expands in all directions, not just upwards. Since you're at WalMart, I'd buy several gallons of RV antifreeze (the pink stuff) and drop it into the black and grey tanks. That will lower the freezing temperature of your liquids to the safe point.
I think I'd travel north as long as it was above freezing, then empty the tanks and add the antifreeze.

Brrrr, it's cold here this morning.....60 f.