frozen line between house and tank

A few years ago were gone for a month during winter and the line from our house to the septic tank froze. Since then I have dug up that line and insulated around it. We haven't had that problem again, but we haven't had the same conditions (very cold and little snow) while we've been away.

We plan to be gone longer this winter and I'm concerned about having a freezing problem again. I'm considering connecting a water supply line from either the cold water (likely about room ambient temperature) or the hot water supply to the drain near the exit from the house and have it controlled by a solenoid valve and a timer so it would run water for a period of time several times a day. Make sense?? Or could there be a problem having too much clean water flowing through the system?

Any thoughts would be appreciated.

Thanks, Dave

hot water freezes faster than cold water..i dunno why, physics thing

if you are not home, and no water is being used, then the pipe should not have any water inside of it to freeze
the pipe is sloped, gravity drains

i am confused as to your problem.

but..if you think you need to heat your unused drain pipe
buy some heat trace wire, fish it down the pipe,
you are good to go...do not forget to remove the wire after vacation, so you can use it again next year

https://www.supplyhouse.com/Easy-He...ping&msclkid=07d9191b77391093a0bc448c32365890

The heat from the septic tank should keep the line from freezing. I have seen this happen but in most cases, they had the septic tank pumped in the winter.

The rich folk over at Sun Valley have a foam insulator with a heat trace wire that is on the bottom of the pipe.

Us poorer folk put sides and a cap of 4-inch poly-iso foam installation. Six inches below the invert, a foot outside the haunch, six inches above the crown.