Minnesota Winter Plumbing: What the Frost Depth Actually Means for Your Pipes
Open 24 hours a day, every day of the year. Call 952-521-0880.
Minnesota ground frost reaches a median maximum depth of 20.0 inches, according to Minnesota DNR climate data, with a median frost-in date of November 23 and a median frost-out date of April 10. Pipes in garages, rim joists, and uninsulated crawlspaces freeze first. Charli’s Emergency Plumbing takes frozen and burst pipe calls any hour at 952-521-0880.
Twin Cities ground frost, in inches below the surface
How Deep Does Frost Actually Go Here
Twin Cities ground frost has reached a median maximum depth of 20.0 inches, according to Minnesota DNR climate data. The same DNR record puts the median frost-in date at November 23 and the median frost-out at April 10. The pipes most exposed to that cold run through garages, rim joists, and other uninsulated spaces.
That figure is a median across 25 winters at the DNR’s long-running measurement station, not a single bad year. Twenty inches is deep enough to reach past a shallow line and into territory a lot of South Metro homes were never fully insulated against, especially anywhere a pipe run leaves the heated part of the house.
A median also means some winters run shallower and some run deeper. Twenty inches is the middle of the distribution, not a ceiling, which is exactly why a house that stayed dry through a mild winter can still lose a pipe the first time a real cold snap arrives.
The stakes behind that number are real and measured too. Water damage and freezing claims averaged $13,954 per claim nationally from 2018 to 2022, according to the Insurance Information Institute, with the underlying data attributed to ISO, a Verisk Analytics business. Water damage and freezing is also the second most common cause of homeowners insurance claims industry-wide, behind wind and hail, affecting about 1 in 60 insured homes each year. That is not a Minnesota-specific figure, but Minnesota’s frost depth is exactly the kind of regional risk that feeds a national average like this one.
The part of the year the ground is frozen
Where South Metro Pipes Are Most at Risk
Four places leave a pipe closer to outdoor air than the rest of the house.
Garages.
An attached garage is rarely heated to the same standard as the house, and a supply line or a hose bib running through one sits closer to outdoor temperatures than most homeowners expect.
Rim joists.
The band of framing where the foundation meets the first floor is thin, often under-insulated, and a common pipe route. It is also one of the harder spots to insulate after the fact without opening a wall.
Uninsulated crawlspaces.
A vented crawlspace can run close to outdoor air temperature all winter. A pipe crossing one without foam sleeve insulation is exposed the entire season, not just on the coldest nights.
Exterior walls.
Any supply line run inside an exterior wall, common in additions and in homes plumbed before insulation standards tightened, has less protection than a line inside an interior wall.
A pipe in any of these four spots is worth checking before the frost-in date each year, not after the first freeze warning arrives. Foam pipe sleeves are cheap insurance in all four locations. In a garage or crawlspace that still freezes despite insulation, UL-listed heat tape, plugged in and left connected through the coldest months, is the next step up. A thermostat left at a normal setting, even while the house is empty, and cabinet doors opened under sinks on exterior walls during a hard cold snap both cost nothing and matter more than people expect.
Call 952-521-0880. We are open right now.
Why a Dripping Faucet Is Not Overkill
A frozen pipe usually does not burst where the ice forms. Research from the Building Research Council at the University of Illinois found that pressure builds in the water trapped between the ice blockage and a closed faucet, and that trapped pressure is what ruptures the pipe, often at a point where no ice has even formed. Source: Gordon, "An Investigation into Freezing and Bursting Water Pipes in Residential Construction," Building Research Council Research Report 96-1, 1996.
That finding corrects the folk explanation most people repeat, that ice simply expands and pushes the pipe wall apart until it splits. It does not work that way. The danger comes from a closed system: ice forms a plug somewhere in the line, more ice keeps building behind it, and the water trapped between that plug and a shut valve or a closed faucet has nowhere to go. Pressure climbs until something gives, and it is often the weakest point in the run, not the frozen section itself.
That is the whole reason a slow drip is real advice and not folklore. Moving water resists freezing better than still water, and a drip also keeps one end of the line open, so pressure never has a fully closed system to build inside. It costs a little water. It is a fair trade against a burst line at 2 a.m.
There is a second reason a drip helps that has nothing to do with pressure. Moving water carries a small amount of heat with it as it travels toward the tap, and that little bit of warmth is often enough to keep the water right at the fixture end from ever reaching freezing, even when the pipe further back is already cold enough to be at risk.
One caveat worth stating plainly: a drip does not prevent every freeze. If a line is already blocked by ice before you start dripping the faucet, the drip cannot reach past the blockage. That is exactly why the shutoff step below still matters, even on a line you have been dripping all week.
Where a frozen pipe splits
When to Shut Off Outside Spigots and How
Every outdoor hose bib on a South Metro house is a straight shot for cold air into the plumbing behind it, and it is worth handling before the ground starts to freeze, not after.
Disconnect and drain every garden hose.
A hose left attached traps water in the bib itself and defeats the point of everything else on this list, including on a frost-free sillcock, whose freeze protection depends on the outside portion of the fixture staying empty.
Find the interior shutoff for that spigot.
Most Minnesota homes have a dedicated valve inside, usually in the basement or a utility space, close to where the line passes through the exterior wall.
Close that valve.
Then go back outside and open the spigot to drain whatever water is left in the line between the valve and the outdoor fixture.
Leave the outdoor spigot open through the winter.
A closed spigot on a drained line does nothing useful. An open one lets any residual water expand outward instead of against the pipe.
The DNR’s median frost-in date, November 23, is a reasonable prompt to have this done every year. It is not a deadline to race. Pipes freeze on the cold snaps that arrive before the calendar catches up, not on schedule.
If a Pipe Already Froze
Shut off the main water valve before you thaw anything. A frozen pipe often hides a split that only shows itself once the ice melts and water starts moving through it again, and you want that valve already closed when it does.
Open the nearest faucet on the frozen line, then warm the pipe gently. A hair dryer works. A torch never does, both for the fire risk and because uneven, high heat is exactly the kind of shock that can turn a hidden crack into a real break.
Not every pipe material behaves the same way under a freeze. PEX tolerates a freeze better than rigid copper or galvanized pipe, since it flexes slightly as ice expands inside it, but flexible is not the same as immune, and a fitting or a valve on a PEX line can still fail even when the pipe itself survives. Older galvanized lines, common in South Metro homes built before the 1980s, are the least forgiving of the three and the ones most likely to need a full section replaced rather than a single patch.
Even a frozen line that thaws on its own without a visible leak is worth a second look. A section of pipe that just spent a night at freezing and below has been through real stress, and a hairline crack does not always show itself the first time water flows past it again. If a pipe froze once this winter, it is worth having it checked, not just waited on.
If the pipe already split, or you cannot find where it is frozen, that is a call, not a project. See frozen pipe repair for what that visit involves, or is this a plumbing emergency if you are not sure whether tonight is the night to make the call.
Close the main, then call 952-521-0880.
Open
handle along the pipe
Closed
handle across the pipe
To close the valve, turn the lever a quarter turn, until the handle sits across the pipe.
Open
Closed
A round-handled gate valve takes several full turns.
When a pipe gives way
When a pipe gives way, close the main first.
Then call 952-521-0880, any hour, all season.