Pipe Freeze Calculator
Enter the forecast low and where the pipes run. The calculator scores the freeze risk and turns it into tonight actions: which faucets to drip, how much foam to add, when heat tape earns its outlet.
Pipes rarely freeze at 31 F and rarely survive a hard freeze bare in an exterior wall - the 20 F line is where plumbers and the Red Cross agree trouble starts. The risk depends on three things: how cold, where the pipe runs, and what covers it. That is exactly what this page scores.
How to use
- Forecast low first - the number on tonight row, not the daytime high.
- Pick where the vulnerable pipe runs: exterior wall, garage or crawlspace, cabinet, open heated space.
- Pick the insulation: bare, foam sleeve, or heat tape. The score and the action list update as you type.
Frequently asked questions
At what temperature do pipes freeze?
Water freezes at 32 F, but pipes inside walls get a buffer from the house - trouble starts around 20 F, especially for bare runs in exterior walls or unheated garages with wind on them. The calculator scores your exact setup instead of quoting the average.
Should I drip faucets tonight?
Drip when the score says HIGH or MEDIUM: a pencil-thin stream on every cold-line faucet, and open the cabinets on that wall so warm room air reaches the pipe. Moving water and warmer air are the whole trick.
How long does it take a pipe to freeze?
A bare pipe in an exterior wall can freeze within about six hard hours below 20 F; a foamed or indoor pipe shrugs off the same night. That is why the action list is about tonight, not next week.
Does foam pipe wrap actually work?
Foam sleeves buy roughly a few degrees of buffer and pay for themselves in one cold snap; heat tape plus foam is the setup that survives the deep freezes. The foam-wrap figure in the calculator is the exposed footage most houses need on one wall run.