Frozen Anti-Freeze??

[LeonW]

I went to visit the trailer today, and pull the batteries out for the winter. While I was putzing around, I noticed that the anti-freeze I had left in the toilet bowl (maybe ½-1 cup?) was frozen solid. luckily I did the winterizing by blowing out the lines with compressed air, and then pouring antifreeze down the drains and into the gray and black water tanks. So I don't think the water lines will freeze, and if the trap under the sink freezes, I think I could replace it fairly easily.

But I was very surprised to see the pink stuff frozen. I thought it would remain liquid until -50 like it says on the bottle. I didn't dilute the stuff. Do you think I could have gotten a bad batch? How worried should I be?

The temperature here this morning was about 10 degrees fahrenheit.

Thanks much.