Which Pipes Freeze First and How to Protect Them (Landlord Guide)

TL;DR: Pipes running through exterior walls, unheated crawl spaces, attics, and garages freeze first, usually once outdoor temperatures fall below 20°F. Insulating exposed lines, keeping a trickle of water moving, and sealing air leaks prevent most freeze events; if a pipe still bursts on a rental property, the repair cost may be deductible as an ordinary repair or, in some cases, as a casualty loss — confirm the current rules with a CPA before filing.

_Last reviewed: July 2026 · 7 min read_

A frozen pipe rarely announces itself until water is already on the floor. If you own a rental and the tenant is away, or the unit sits vacant over winter, the damage can pile up for days before anyone finds it. Here's which pipes go first, how to stop it, and what happens tax-wise if you can't.

Okoniq Property Hub logs maintenance visits, insulation upgrades, and repair costs by unit, so you have a clean paper trail if you ever need to support a repair deduction or a casualty loss claim.

Which pipes freeze first in a home?

Pipes located outside the building's heated envelope freeze first. That means lines running through exterior walls, unheated crawl spaces, attics, garages, and basements with drafty vents are the first to go, because they're exposed to outdoor temperatures with little or no insulation around them.

Kitchen and bathroom supply lines on outside walls are a common failure point in older homes, especially where insulation was added after the plumbing was roughed in. Hose bibs, pool supply lines, and any pipe running along an unheated garage ceiling are also high-risk. Once ambient temperatures near a pipe drop below roughly 20°F for several hours, the water inside can freeze even though the room itself feels tolerable to a person standing in it, because the pipe is colder than the air around the occupant.

If you manage more than one property, it helps to walk each unit before the first hard freeze of the season and note where pipes run close to an exterior wall. Landlords who've dealt with a burst line once tend to build this into their chart of accounts as a recurring seasonal maintenance line item, so the cost of prevention gets tracked the same way as any other repair category.

Why do frozen pipes burst, and how much damage can they cause?

Frozen pipes burst because ice expands inside the pipe and builds pressure between the ice blockage and a closed faucet, not because the ice itself cracks the metal or plastic directly. Water expands roughly 9% in volume when it turns to ice, and that expansion has nowhere to go in a sealed pipe, so pressure climbs until the pipe wall gives out, usually at a joint, fitting, or the weakest section of the line.

The damage isn't limited to the pipe itself. A burst line can run for hours before anyone notices, soaking flooring, drywall, insulation, and sometimes a ceiling below. In a vacant winter rental, that discovery window can stretch to days. Repair costs for a single burst-pipe event on a rental unit commonly run into the thousands once you count plumbing repair, drywall, flooring, and mold remediation together, though the exact figure depends heavily on how fast it's caught.

How can landlords prevent pipes from freezing in vacant or rented units?

Prevention comes down to insulation, heat, and moving water, in that order of importance. Foam pipe sleeves or heat tape on exposed lines in crawl spaces, attics, and exterior walls are the cheapest and most effective fix, and they're a one-time install that pays for itself the first winter it's needed.

Keep the thermostat set no lower than 55°F in any occupied or vacant unit during freeze risk periods, and open cabinet doors under sinks on exterior walls so warm room air can reach the pipes. On especially cold nights, letting a faucet run at a slow drip keeps water moving through the line, which resists freezing far better than standing water. For units that will sit vacant for weeks, shutting off the main water supply and draining the lines removes the risk entirely.

| Approach | Occupied rental | Vacant winter unit | |---|---|---| | Pipe insulation / heat tape | Recommended, low cost | Recommended, low cost | | Thermostat minimum | 55°F+ | 55°F+ (not below) | | Faucet drip during cold snaps | Effective, tenant-dependent | Not applicable if drained | | Shut off + drain water main | Not practical | Best protection available |

Sealing air leaks around pipe penetrations, sill plates, and exterior wall penetrations also matters more than most landlords assume, since a small draft hitting a pipe directly is often what tips it from "cold" to "frozen."

Is frozen pipe damage tax-deductible for landlords?

Repair costs to fix a burst pipe on a rental property are generally deductible as an ordinary and necessary repair expense in the year paid, because you're restoring the property to its prior condition rather than improving it. This is the same logic covered in Okoniq's capitalize vs. expense decision tree: if the work fixes damage without adapting the property to a new use or materially bettering it beyond its original condition, it's typically an expense, not a capital improvement.

Small repair invoices — a plumber's visit, a section of pipe, patch drywall — may also qualify under the $2,500 de minimis safe harbor if you've made that election for the year, letting you deduct the full invoice amount without running a capitalization analysis on each line item.

Separately, a sudden and unexpected event like a pipe bursting can sometimes be treated as a casualty loss rather than a routine repair, particularly when the loss involves property damage beyond simple wear and tear. The rules for casualty losses on rental property differ from the rules for a personal residence, and the personal-use casualty loss deduction has specific requirements tied to state or federally declared disasters starting in 2026 under recent legislation. Because the treatment depends on the specifics of the event and your entity structure, read Okoniq's guide to casualty loss deductions for rental property and confirm the current requirements with a CPA before you file.

What should you do the moment you find a frozen or burst pipe?

Shut off the water main immediately, then open the nearest faucet to relieve pressure in the line before it fails if it hasn't already. If water is actively flowing from a break, cutting power to any nearby electrical outlets or fixtures is worth doing before you touch anything, and calling a licensed plumber is the right move rather than attempting a DIY fix on a pressurized line.

Photograph the damage before cleanup starts. Whether the repair ends up as a routine expense or a casualty loss claim, dated photos, the plumber's invoice, and a note of when the freeze event happened are exactly what an auditor would look for if the deduction is ever questioned.

FAQ

At what temperature do pipes actually freeze?

Water freezes at 32°F, but pipes running through exterior walls or unheated spaces are commonly at risk once sustained outdoor temperatures drop below about 20°F, because the pipe itself sits colder than a room's ambient reading.

Can a pipe freeze without bursting?

Yes. A pipe can freeze solid and simply stop water flow without bursting, which is why a "frozen but not broken" pipe should still be thawed carefully with a hair dryer or heat wrap, never an open flame, and monitored for leaks as it thaws.

Is a burst pipe covered by homeowners or landlord insurance?

Most landlord and homeowners policies cover sudden, accidental water damage from a burst pipe, but many exclude damage caused by inadequate heat in a vacant property or preventable neglect, so check your policy's vacancy clause before assuming coverage.

Do I need a permit to repair a burst pipe?

Simple like-for-like pipe repair usually doesn't require a permit, but repiping a section, moving a line, or repairs tied to a larger renovation often do, depending on your local code, so confirm with your municipality before starting larger work.

How do I document a frozen pipe repair for tax purposes?

Keep the plumber's itemized invoice, dated photos of the damage, and a note of the repair date and cause, then record the expense in the correct account so it's easy to defend the deduction category if it's ever reviewed.

<div class="glass rounded-2xl p-5 mt-7 max-w-4xl border border-red-400/30 bg-red-500/5"> <div class="flex items-start gap-3"> <span class="text-2xl flex-shrink-0">⚠️</span> <div class="flex-1 min-w-0"> <p class="text-red-200 text-sm font-bold">Not tax advice</p> <p class="text-slate-300 text-xs mt-1 leading-relaxed"> This post assumed pipe damage occurred on a rental property with documented repair costs, and it does not account for your specific tax bracket, entity structure, state disaster declarations, personal-residence casualty loss limits, or legislation after July 2026. Tax rules change and depend on your specific situation. Talk to a licensed CPA before acting on anything here, and confirm current figures on IRS.gov. </p> </div> </div> </div>