Well that may be a good sign. Up here it's only super cold when the sky is clear. If it is going to snow it needs to cloud up. That will raise your temperatures a bit

Pex not busting is a bunch of bull, lol. We've had 2 pex lines freeze and split already this winter and it's not got below 25 yet.

That's why when the Zamboni does the ice ovah....it lays down hot water..

It freezes fastah

Open cabinet doors crank heat, put a fan facing the water line. Put some poly around the house and draped on the ground then cover and bank with snow. When you do find the frozen spot get a small milk house heater and put in the cabinet when it gets cold. also seal the windows and fix the door seals. I grew up in mobile homes and old houses with crawl spaces. It was a full time job keeping the water going.

X 2

The two we had the pex line itself split open right in the middle of the line, not even near a fitting.

I think I found it!, I use a heat gun all the pex was 60 to 52 but the area behind the bathroom sink was 29. So tomorrow I'll pick up some heat tape.

Is it pex or polybutalane? What color is it?

Try hitting the area with a fan....

Leave the cabinet open if you can to get some heat to it.

Open the cabinet,, point a fan into the space. Crank the heat to the house, should do the trick if it's frozen where it comes into the cabinet. If it's deeper in the wall it may take a bit. Single digits aren't very cold should be able to protect against that. Do you have a high wind blowing on the wall the line is froze?

What kind of house is it? Slab on grade? Do you have a basement? Crawl space? Mobile home? ? Is this a new house? Or did you just move in there? What was the temperatures when it froze up?

Heat tape won't really do any good unless you can get at the Frozen location.

Don’t go to bed with the faucet wide open. You might end up with a flood on your hands.

Lots of times here it’s the wind direction more than the actually temp. -20 with north wind no problem. -10 with an east wind and I have to have a fan on upstairs bathroom wall.

Stick built on a concrete slab. The froze line has to be in the bathroom that's where it come out of the furnace room and that's 70. Or the froze line could be under the kitchen cabinet.

Doesn't really matter what the temp of the room is, it only matters what the temp is where it's froze. I know that sounds a little simplistic but it is what it is. I doubt if its frozen in the cabinet,it's most likely in the wall. If you think it's froze in the cabinet put a hair dryer on the line, it will thaw out in seconds to a minute or two. Do you have any kind of a electric space heater? Put it blowing into the cabinet, that will thaw it out if it's frozen in the cabinet or maybe quite near to it.

Was the wind blowing on the wall that contains the water line? Is it a new house? You are going to have to figure out a way to stop it from happening again or learn to live with it. I have a friend with a slab house, when the wind is right his water line will freeze and we typically have to thaw it out with steam.

Last year I had two short, like 3” pieces of 3/4” pex freeze and split between two plastic elbows. And the elbows were fine. I couldn’t believe it. It is the pex you expand with the tool and ring. I wonder if since they were so short the flex was taken out when expansion tool was used?

Trapset I expect the entire 3 inch piece froze thus not allowing for enough expansion.

Pex is more flexible than copper or PVC. It will take freezing better as water expands as it freezes, but Pex is not immune to bursting.

Hot water does not freeze faster than cold water. Hot water looses heat faster than cold water until it IS cold water because the heat transfer rate is a function of the temperature difference. Then the previously hot water IS cold water and looses heat based on its temperature until it freezes, just like cold water.

If I had to guess what your problem is I would say that the myth that Pex is immume to freeze burst led your plumbing contractor to be lazy and put lines too close to the outer wall instead of insulating them from the outside properly. Once you find and hopefully thaw the frozen lines unburst, put some foam insulation between them and the outer wall. DO NOT just insulate the lines, insulate from outside ONLY. You want heat from inside to get to the lines.

In the event that White's Bernoulli explanation is the issue and the frozen plug is at a penetration, use steel wool to stop air flow between the water line and the wall/floor hole where it penetrates. The science behind his explanation is sound but I think it is a secondary effect. That's no reason to ignore it, sometimes small effects are all the difference.

Open all cabinet doors and turn the heat up in the house. It's coldest in the cabinets when doors are shut.