How to Tell if Your Pipes Are Frozen: 6 Signs to Check

Why Minnesota Winters Are Especially Hard on Pipes

Water expands about 9% when it freezes. Most residential pipe materials cannot absorb that pressure, and once a pipe is already frozen, there is a roughly 50% chance it has already cracked.

The freeze threshold is lower than most homeowners expect. Pipes begin to freeze when the air around them drops to 20°F, and at that temperature, unprotected pipes can freeze in under six hours. At 10°F or below, that window shrinks to under two hours. The Twin Cities regularly hits both thresholds in any given winter.

Minnesota also sets strict burial requirements for water lines. Minnesota Plumbing Code Rule 4714.0609 requires water service lines to be buried at least 12 inches below the local frost depth. In the Twin Cities metro, that means at least 54 inches deep. Minneapolis specifically requires 7 feet to the top of the pipe. Even with proper burial, pipes in unheated interior spaces, garages, and crawl spaces have no such protection. A single night of extreme cold is enough to freeze an exposed pipe.

How Do You Know if Your Pipes Are Frozen?

The clearest sign is no water from a faucet on an exterior wall. Other signs include frost on an exposed pipe, an unexplained pressure drop, unusual sounds from the walls, sewer odor from multiple drains, and visible water damage. The first four are early warnings. The last two mean the problem has already crossed into damage territory.

The six signs below appear in order of urgency, from the earliest warning to the point where you need to shut off the water immediately.

Sign 1: What Does No Water Flow From a Faucet Mean?

No flow from a faucet, or a drop to a bare trickle, is the most common early sign of a frozen supply line. Ice has blocked the pipe between the main and that fixture. One affected faucet is a warning. Two or more faucets with no flow on the same side of the house points to a significant freeze and a real risk of a burst.

Before concluding it is a freeze, check a few things:

• Is the main water supply to the house on?
• Which faucets are affected? Fixtures on exterior walls or on the same side of the house point to a freeze in that wall cavity.
• Is cold water affected but not hot, or vice versa? This can help narrow the frozen section.

A single faucet with no flow can be a clog, a failed valve, or a freeze. Complete loss of flow from multiple fixtures on an exterior wall on a night below 20°F is a freeze until something rules it out.

Sign 2: Is Frost on an Exposed Pipe a Confirmation of a Freeze?

Yes. Frost on the outside of a copper or PEX supply line is direct visual confirmation that section is frozen. Check exposed pipes in basements, crawl spaces, and garages first, because those are the highest-risk locations.

Run your hand along the pipe if you can safely reach it. The frozen section will feel dramatically colder than the pipe on either side. Look for a slight bulge or discoloration at the freeze point. Both are signs of internal pressure building. A visible crack or split in the pipe means it has already burst. Skip to Sign 6.

Insulated pipes can also freeze. If insulation has shifted, torn, or gotten wet and compressed over time, it has lost its thermal protection. Check that insulation is snug and unbroken along the full pipe run before any extreme cold event.

Sign 3: What Does Low Water Pressure Mean on a Cold Morning?

A partial freeze narrows the pipe’s interior without blocking it completely. The result is noticeably lower pressure at the faucet, even though water still flows. On a night that dropped below 20°F, an unexplained pressure drop at a faucet on an exterior wall is a freeze signal worth taking seriously.

The key is location. A failing pressure-reducing valve (PRV) drops pressure at all fixtures throughout the house. A localized freeze drops pressure only at fixtures near the frozen section. If the pressure problem is isolated to one side of the house, or one floor, a freeze in that area is the most likely explanation.

This sign often appears before complete blockage. Catching it here, before flow stops entirely, gives you the most options.

Sign 4: Are Cracking or Banging Sounds From the Walls a Sign of Frozen Pipes?

They can be. Expanding ice inside a pipe exerts pressure on fittings, elbows, and connection points. That pressure can produce knocking, cracking, or a low groan from behind the drywall. Combined with any other sign on this list, unusual sounds on a night below 20°F are a strong indicator.

Listen for:

• A dull knocking or banging from inside a wall or floor cavity
• A cracking sound similar to ice shifting under pressure
• A low groan or hissing from behind a finished wall

These sounds are easy to dismiss as a house settling. On a night following a temperature drop past 20°F, do not dismiss them without checking. Do not wait until morning.

Sign 5: What Does Sewer Odor From Multiple Drains Mean in Winter?

Sewer odor from more than one fixture at once, especially paired with multiple slow drains or a gurgling toilet on a flush, points to a frozen drain line. This is a different problem from a supply-line freeze, and the fix is different too.

Buried sewer laterals below frost depth typically do not freeze. The vulnerable points are the exterior cleanout cap, which can freeze shut, and shallow interior drain traps in unheated spaces. When a trap freezes, sewer gas cannot vent properly and backs up through the nearest fixture.

The pattern is the key to reading this sign correctly. One slow drain is almost always a clog. Multiple slow drains throughout the house, sewer odor from several fixtures at once, and a toilet that gurgles when flushed: that combination points to a frozen trap or a block in the main stack.

Do not run more water if you suspect a frozen drain. Running water into a frozen or blocked drain line backs it up further. Call a plumber. For more on reading the difference between a drain clog and a full sewer backup, see our post on sewer backup vs. drain clog: how to tell the difference.

Sign 6: What Do Water Stains, Soft Drywall, or Pooling Water Mean?

This is not a warning sign. This is damage that has already happened. Shut off the main water valve immediately, before anything else.

Shut off the main if you see any of these:

• A brown or yellowish water stain on drywall, a ceiling, or a floor that was not there before
• Drywall that is soft, bubbling, or visibly warped
• A wet spot on an exterior wall on a cold day with no surface explanation
• Water pooling under a cabinet on an exterior wall

The pipe has cracked or burst. Shutting off the main stops additional water from flowing through the break. Know where your shutoff is and that it actually turns before you need it in an emergency. For a quick refresher, see our guide on finding and testing your main water shutoff valve.

After the main is off, call a plumber. Do not try to thaw the pipe yourself once you see visible damage. The crack may be upstream from where the staining appears, and flowing water through the damaged section extends the flooding. If the freeze led to significant pipe damage, our team can walk you through burst and frozen pipe repair options for your Twin Cities home, including financing for larger repairs.

Where Should You Look First for a Frozen Pipe?

Start with cabinets under sinks on exterior walls. Then check the basement where the main line enters the house. After that, check the garage if any supply lines run through it, then the crawl space. Those four locations cover the highest freeze-risk areas in most Twin Cities homes.

Here is the full triage order:

1. Exterior-wall cabinet pipes. Kitchen sinks and bathroom vanities on outside walls are among the most common freeze points in Minnesota homes. Open the cabinet doors during extreme cold to let warm air reach the pipes. Check these first.

2. Basement entry point. The water main enters through a basement or crawl space wall. That penetration point is where outdoor temperature meets the interior of the home. Older homes, especially those built before 1980, often have minimal insulation at this spot.

3. Garage. Any supply lines running through an attached or detached garage see near-outdoor temperatures whenever the space is unheated. Hose bib supply lines frequently route through garage walls and are easy to overlook until flow stops.

4. Crawl space. An unheated crawl space in a Minnesota January sits well below 20°F. Any supply line running through an uninsulated crawl space is at high risk. Check that floor insulation above the space is intact and that there is a heat source keeping the area above freezing.

5. Attic (less common, but real). In some older Twin Cities homes, supply lines pass through attic space. An uninsulated attic in midwinter can be as cold as outside. If a faucet on an upper floor has no flow and all other areas check out, look at whether a supply line routes through the attic.

What Minneapolis and Twin Cities Homeowners Need to Know About Their Service Line

Most homeowners focus on the pipes inside the house. The water service line running from the street to the meter deserves equal attention, and in Minneapolis, it is entirely the homeowner’s problem if it freezes.

Minneapolis property owners own the entire water service line from the city main to the meter, including the curb stop. Thawing and repair costs fall to the owner, not the city.

If the service line freezes, the city recommends running a pencil-width trickle of cold water from the lowest faucet in the house until the ground thaws. A pencil-thick drip is roughly 1 gallon every 4 minutes. Bloomington MN estimates that running water continuously to prevent a freeze adds approximately $100 per month to a water bill. That is considerably less than a service line repair.

There is also a useful early warning to watch for: if your cold tap water measures below 40°F, it is a sign to start dripping before the line freezes. A probe thermometer at the cold tap can catch this before you lose flow entirely.

If the trickle method does not restore flow within an hour, call the Minneapolis water emergency line at 612-673-5600. Then call a licensed plumber.

Homeowners in St. Paul, Bloomington, Maple Grove, and the rest of the metro should check with their own utility on service line ownership rules. The pattern is similar across the region, but each municipality sets its own policy on where city responsibility ends and homeowner responsibility begins.

When Should You Call a Plumber Instead of Thawing a Pipe Yourself?

Call a plumber if two or more faucets have no flow, if you cannot locate the frozen section, if the pipe runs inside a finished wall or floor, or if there is any visible water damage. A frozen pipe already has a roughly 50% chance of having cracked. Thawing a cracked pipe without seeing the damage can turn a small break into a significant flood.

Use this escalation guide:

Proceed carefully yourself (exposed pipe, no damage visible):

• One faucet with no flow, all others normal
• Frost visible on an exposed pipe you can safely reach
• No visible cracks, splits, bulges, or water staining nearby

Call a plumber:

• Two or more faucets with no flow
• Cannot locate the frozen section
• The pipe runs inside a finished wall, floor, or ceiling
• Any sign of water damage: staining, soft drywall, pooling water
• Sewer odor from multiple fixtures at once
• You thawed a pipe and flow did not return

Shut off the main first, then call:

• Visible crack, split, or bulge on any pipe
• Water actively flowing or dripping from a wall cavity
• Water staining on a ceiling or floor that appeared during cold weather

Northern Benjamin Franklin Plumbing is locally owned and operated in the Twin Cities. Our burst and frozen pipe repair team covers the full metro, and our On-Time Guarantee(R) means we arrive in the window we promised. If there is any delay, it’s you we pay!

Call (763) 296-1844 or book online.

What to Do Right Now if You Suspect a Frozen Pipe

Work through this list before going to bed on any night the temperature is below 20°F:

1. Check two or three faucets on exterior walls for flow and pressure.
2. Look at exposed pipes in the basement and crawl space for frost or bulges.
3. Listen at the walls on the cold side of the house for knocking or cracking sounds.
4. Open cabinet doors under kitchen and bathroom sinks on exterior walls.
5. Confirm your main shutoff is accessible and turns freely.
6. If you find no flow at multiple fixtures, or any sign of damage, shut off the main and call a plumber.

A frozen pipe at midnight on a -10°F night can become a burst pipe by 4 a.m. Early detection is what prevents that outcome. For step-by-step guidance once you have located a frozen section, see our post on how to thaw frozen pipes in Minnesota.

If you are not sure what you are looking at, call (763) 296-1844. We will help you figure it out.