Why crawlspace pipes freeze in Clarksville

Why do crawlspace pipes freeze first?

They sit in the one part of the house that is neither heated nor buried. The Red Cross lists supply pipes in unheated interior areas, crawl spaces among them, as the usual trouble spots, along with pipes on poorly insulated outside walls (American Red Cross, archived copy). In a house built over a crawlspace, the supply lines often run through that space, a few feet above bare ground and close to the vents.

Water expands as it turns to ice, and the Red Cross notes that this pressure can split a metal or plastic pipe whatever its strength. The break often shows only after the thaw, when water starts to flow again.

How cold does a Clarksville winter night get?

January lows average 27.8°F at the Clarksville WWTP station, the coldest month of the year in NOAA's 1991–2020 normals (NOAA NCEI monthly normals). December and February average lows of 31.1°F and 30.6°F, both just under freezing. A crawlspace open to that air through vents or gaps follows it down over a long night.

An average low hides the nights that do the damage. Those are the hard-cold ones, shown next.

Which nights put crawlspace lines at real risk?

The nights at 20°F or colder, which come about 16 times a year. January averages 7.0 of them, February 4.1 and December 3.7, with a few stragglers in November and March. A long run of those nights, especially with wind, is when a line near a vent or the rim joist is most likely to freeze.

Across town the counts barely change, so a house near the airport and one near the river face much the same winter. The full year of freezing nights is on our freeze nights page.

How do you protect pipes in a crawlspace?

Insulate them and keep the space warmer. The Red Cross recommends adding insulation to crawl spaces and wrapping both the hot and the cold lines in unheated areas. It names pipe sleeves and UL-listed heat tape or heat cable as options; any heat cable should be installed and plugged in exactly as its maker's instructions say.

• Wrap every exposed run, paying most attention to lines near vents, the access door and the rim joist.
• Look for where the service line comes up through the foundation, which the Red Cross singles out as a common freeze point.
• Seal gaps that let wind blow straight across the pipes.
• Drip the faucet that the crawlspace line feeds on hard-freeze nights, and always on nights at 20°F or below; exposed crawlspace lines can freeze above 20°F.

Who is responsible for the pipe under the house?

You are. CGW's job stops at the meter: past the yoke the meter sits in, the line to the building and all the plumbing inside are the property owner's to keep up (CGW FAQ). CGW's public service-line map lists 3,252 customer-side lines marked "galvanized requiring replacement"; our lead service lines page shows how to look up your address.

Replacing or rerouting pipe is permit work. Within city limits a plumbing permit has to come through a licensed contractor, not the homeowner (City of Clarksville Building & Codes). In the unincorporated county the rules differ, so ask the permit office which applies before any pipe is cut. Details are on our permits and licenses page.

What if a crawlspace pipe freezes or bursts?

If it has burst, shut the main water valve first. For a frozen section you can reach safely, use the gentle heat the Red Cross approves, such as a hair dryer or a heating pad wrapped around the line, or hot wet towels, and leave the faucet open. Use an electric tool only if the crawlspace is dry, plug it into a GFCI-protected outlet, and never stand on wet ground; if water has pooled, stay out until the power is off. If the frozen spot is out of reach or will not thaw, call a licensed plumber.

A burst that ran for hours before anyone noticed will show on the meter and the next bill. Our leaks on the meter page covers the reading.