Tomorrow's project: Dig in and fully check out that heat tape! (I don't like leaving a space heater, even on low, running out there. It's overkill and a little unsafe. Granted a 100 watt incandescent light bulb will work, but, I'm low on those, and would need thermostatic control of such, too....
Good Luck and Merry Christmas!
Looks like you are working through the problem.
Keep us informed of your progress and steps to resolution.
Interesting problem!
Ever leave a bottle of pop in the freezer to get cold, you take it out and does not look to be frozen, untill you pop the cap then it instantly freezes. Same theory. Liquid under pressure has a lower freezing point, when pressure is released, liquid will freeze.
You have chickens, so use a brooder lamp.
>> Can supercooled running water freeze due to a pressure change?
You’d be long dead before water is affected by pressure changes
Be mindful of exterior conditions on any perimeter-based heating such as baseboards.
Easiest and quickest is just turn all your taps inside to run, not drip, might have a higher water bill next month but your water will not freeze.
Best bet - you have air trapped somewhere in the unfrozen part of your piping. This is compressed, and absent pressure from the pump tank will drive water flow from your spigots for a short time. Hot water tank is a good candidate.
You could put in a thermacube (an electric plug that only switches on when it is 35 or below, and then plug a light or small space heater in below. You can use a halogen flood light instead of the incandescent bulb if it is easier to find.
I hate the heat tape, have had it fail multiple times. Must be a quality control issue.
I sympathize with you.
I used to have my water pump and tank in a cinder block bunker and went through something similar every cold snap.
When I tore the old house down and built a new one, I made sure to put the water pump in the well and everything else contained in much warmer location.
But to be fair, it only got down to 2 degrees here.
https://www.iflscience.com/new-record-coldest-freezing-point-of-water-61911
Lots of university dollars chasing record low supercooled water, most can get to around -40 degrees. Usually need high water purity, low agitation, and controlled wall effects to get there.
Flowing water from well or municipal system will have little super cooling. Best theory is rapid depressuring releases dissolved gases, which takes heat from the water. I suspect ice was already forming and causing a narrow, choke spot in the piping. That’s my 40 years of engineering in oil and gas business, where this type of phenomenon can cost millions per incident.
I don’t trust the lightbulb idea because they burn out without warning.
How about two different brands of heat tape at the same time, checking each one every season, or multiple LED bulbs to equal the heat of an incandescent?
If the distance isn’t too great you can put a sensor from your thermometer in the house into the mix, to be able to know everything is working.
Here are some chicken coop heaters.
https://www.amazon.com/chicken-coop-heater/s?k=chicken+coop+heater
Escaping gases will chill the water. That's what happens when you open a very cold can of carbonated beverage. The CO2 escapes, taking heat with it, and the beverage freezes.
To learn more, look for "water phase diagram."
We’re several hundred miles away for the next week. We live on the east coast where it’s very cold but not dangerous. Single digits.
The heat is turned down but above freezing.
My house has a hall valve on the water main. We shut the system down when we leave so if a pipe does crack, it’s not a big deal.
Water is considered to be incompressible. Pressure changes probably not the answer. If it was super-cooled and static, then just adding motion in the form of flow could maybe kick of crystallization.
Shoddy plumbing in shoddy unheated buildings will always fail.
A properly installed plumbing system INCLUDES the necessary construction to prevent freezing.
BUILDINGS MUST BE HEATED!
Heat tapes should NEVER be necessary.