Pipes break first where cold air reaches them and heat does not: crawl spaces, exterior walls, outdoor spigots, unheated garages, cabinets on outside walls, attics and basement rim joists. In an older Alexandria house, those spots can freeze during the first hard cold snap of the season, so the time to protect them is before it arrives.

November is when Northern Virginia gets its first real taste of winter. The days can still feel mild, then a clear, still night drops well below freezing and the plumbing you have not thought about since March gets tested.

Older homes in Old Town, Del Ray and Rosemont tend to have more of these weak spots. Plumbing was often added or rerouted over the decades, and some of it ended up in outside walls, porches, rear additions and crawl spaces that were never meant to stay warm. Newer townhouses in Kingstowne or the West End have their own risks, like hose bibs on a back deck and pipes in a garage below a bedroom.

Why do pipes break when they freeze?

Water expands as it turns to ice. When that ice forms inside a pipe, it squeezes the water that has not frozen yet, and the pressure builds between the ice and the closed faucet down the line. That pressure is what splits the pipe, which is why the break is often a short distance away from the frozen section.

The surprising part is that you usually do not see a leak while the pipe is frozen. The ice plugs the crack. The water comes out when the weather warms, the ice melts and full house pressure pushes through the opening. That is why so many frozen pipe calls come on the first sunny morning after a cold night.

Where do pipes freeze first in an older Alexandria house?

These are the seven places we check first, roughly in the order they tend to cause trouble.

1. Crawl spaces

Many older homes sit partly or fully over a crawl space, and plenty of rear additions were built on one even when the main house has a basement. Vents, gaps around the access door and missing insulation let cold air move freely around the supply lines. A pipe in a crawl space under a kitchen or bath addition is one of the most common places for a winter break.

2. Exterior walls

A sink, toilet or washer on an outside wall usually has its supply lines inside that wall. If the insulation is thin, missing or packed down, the pipe sits right against cold siding or brick. Kitchens and baths in the back of a townhouse are frequent offenders, since they often share a wall with a porch or an alley.

3. Outdoor spigots and hose bibs

A hose left connected over the winter traps water in the spigot and the short pipe behind it. When that water freezes, the split often happens inside the wall, out of sight. You may not find it until you turn the spigot on in spring and water runs into the basement instead of the yard.

4. Unheated garages and utility rooms

Pipes that pass through a garage, an enclosed porch or a laundry room off the kitchen are exposed to outdoor temperatures on cold nights. If the garage sits below a bedroom or bath, there may be supply lines running through its ceiling.

5. Cabinets under sinks on outside walls

A closed cabinet blocks the warm air in the room from reaching the pipes inside it. When the cabinet also sits on an outside wall, the space behind it can get very cold on a windy night.

6. Attics and upper-floor bathrooms

Some older houses have plumbing that runs through an attic or a knee wall to reach a bathroom that was added later. Attics are built to stay close to outdoor temperature, so any pipe up there needs real protection.

7. Basement rim joists and sill plates

Where the floor framing meets the top of the foundation, cold air often leaks in around gaps in the masonry or the band joist. A pipe running along that edge of the basement ceiling can freeze even in a heated basement.

What makes Northern Virginia pipes vulnerable?

Our winters are mild enough that a lot of homes were never built for hard cold, and cold enough that hard cold still comes. Alexandria has a humid subtropical climate. Most winter nights hover near freezing, then a few times a season the temperature drops much lower, often with wind.

Those cold snaps are what catch plumbing off guard. A pipe that has been fine through ten mild winters can split on one windy night in the teens. Homes that sit empty during the day, or houses where the heat is turned way down at night to save energy, are the most exposed.

What does a frozen pipe look and sound like?

Catching a frozen pipe before it bursts gives you the best chance of a quick fix. Watch for these signs on a cold morning:

• A faucet that gives only a trickle or nothing at all, while others in the house work
• A toilet that does not refill after a flush
• Frost on a visible pipe in the basement, garage or crawl space
• A bulge or a small crack in a pipe you can see
• A gurgling or banging sound when you open a tap
• An odd smell from a drain, which can mean the line is blocked by ice

If you see these signs, leave the faucet open a little so water can flow once the ice starts to melt, and shut off the main water valve if you think the pipe has already cracked.

First freeze checklist for Alexandria homeowners

Run through this list on a mild weekend in early November, before the first hard cold night.

• Disconnect and drain garden hoses. A connected hose traps water in the spigot, where it can freeze and split the pipe inside the wall.
• Shut off and drain outdoor spigots that have an indoor valve. Closing the inside valve and opening the outside tap empties the section that is most exposed.
• Find your main water shutoff and make sure it turns. You will need it fast if a pipe breaks, and older valves can stick.
• Look at the pipes in your crawl space. Exposed lines with no insulation, or with sagging foam sleeves, are the ones to fix first.
• Seal gaps around the crawl space door and vents. Blocking drafts keeps cold air off the pipes.
• Add foam pipe insulation where you can reach it. Basement ceilings, garages and utility rooms are easy places to start.
• Check the rim joist area in the basement. Daylight or a cold draft there means air is getting to anything that runs along that wall.
• Plan to open sink cabinets on cold nights. Letting room air reach the pipes helps on outside walls.
• Keep the heat steady overnight. A big nighttime setback leaves the coldest parts of the house even colder.
• Set the thermostat before you travel. The American Red Cross recommends keeping the heat at no lower than 55 degrees Fahrenheit when you are away during cold weather.
• Know which taps to drip. A slow drip from the faucet farthest from the main, or on the coldest wall, keeps water moving on the coldest nights.

How do you thaw a frozen pipe safely?

If a pipe is frozen but not cracked, you can usually thaw it yourself. Open the faucet it feeds so melting water has somewhere to go. Then warm the pipe gently with a hair dryer, a heating pad or towels soaked in warm water, working from the faucet end back toward the frozen section.

Never use an open flame, a torch or a propane heater. That is a fire risk in any house and a serious one in a crawl space full of old wood framing. If you cannot reach the frozen section, or you cannot tell where it is, it is time to call a plumber.

What should you do if a pipe bursts?

Move quickly, but safely. These steps limit the damage while help is on the way.

1. Shut off the main water valve.
2. Turn off the power to any room where water is near outlets, cords or the electrical panel, if you can reach the breaker panel on dry ground.
3. Open faucets to drain the remaining water from the lines.
4. Take photos and video of the break and every wet area before you move things.
5. Move rugs, furniture, electronics and boxes out of the water.
6. Call a plumber to repair the pipe, and call your insurance company to ask what your policy says.

Then think about what you cannot see. Water from a burst pipe runs along subfloors, soaks into the bottom of drywall and drips through ceilings to the level below. In an old house with plaster walls and wood floors, it can settle into places that look dry from the room.

Why does fast drying matter after a winter pipe break?

Wet building materials do not dry well on their own in a closed-up house. The EPA advises drying wet materials within 24 to 48 hours to help prevent mold growth, and winter makes that harder because windows stay shut and cold walls dry slowly.

A restoration crew measures moisture in floors, walls and ceilings, extracts standing water, and sets up air movers and dehumidifiers sized to the space. In older Alexandria homes, the goal is often to dry original plaster and hardwood in place rather than tear them out, and that takes daily readings and patience.

Get ahead of the first freeze

A few hours of prep in early November can save you from a wet basement in January. If a pipe does break in your Alexandria home, contact ServiceMaster NCR. We are available 24/7 to remove the water, dry the structure and help you document the damage.