It has been really cold in DC lately. My thermostat is broken, so it goes to 77 degrees no matter what I set it to. I tried to get it fixed, but it ended up being a waste of $50 because they just cleaned the boiler, although I told them over the phone what the problem is. So I decided to just ignore it because winter is almost over anyway. I turn the heat off at night since I'm under my blankets, so it was 46 degrees in the house when I woke up yesterday morning.

I noticed that the cold water to the entire upstairs bathroom wasn't working. I left the heat on all day, and the faucet and toilet cold water line thawed out. But the tub cold water line is still not working, now a full day later.

I've tried the hair dryer thing, and next I'm thinking about using the wet vac on the faucet to see if an air pocket is the problem. My Dad thinks this is a bad idea. Is it?

Anyway, in the mean time I've been leaving the faucet open so pressure doesn't build up and also so I can hear it when it hopefully comes back on. But after reading some more stuff on line I'm worried that leaving the faucet open means there is still water trying to come through the pipe and that will burst it.

So long story short, if a cold water line is frozen do I leave the faucet open or closed?

Thank you!

  • The line will be under pressure from the incoming supply, leaving the faucet open doesn't increase pressure. When my cold water tub gets frozen I run the hot water at just a trickle so there's hot water in the line. Since the hot water is close to the cold water, at least in the same wall cavity, it helps heat up that cavity to the point where the cold water line thaws out. At night leave the cold water tap open a small bit and Commented Feb 17, 2015 at 14:53
  • Ok, I'm going to try letting the hot drip. Thanks!
    – Jasmine B
    Commented Feb 17, 2015 at 15:09

1 Answer 1


It makes absolutely no difference whatsoever to the freezing condition if you leave the faucet open or not.

If a faucet is left open BEFORE it freezes, it can prevent freezing because running water does not freeze.

The only way to thaw it is to find the area that is frozen and heat it with a warming strip or a hair dryer or a propane torch or whatever. Try not to start a fire. If you use a hair dryer it can take HOURS to thaw a water line, even if it is blowing at high right at the frozen spot. Also, a hair dryer will only work if the line is frozen in one specific spot. If, say, 3 feet or 4 feet of piping are frozen, there is no way a hair dryer will do anything (at least in a day or two).

  • Ok, so I guess I'm just going to have to leave all the other faucets dripping and hope heating the house eventually thaws it out. Thanks!
    – Jasmine B
    Commented Feb 17, 2015 at 21:52
  • @JasmineB If the pipes are inside walls, all you can really do is heat the house. If you have a cold room or basement, try putting a space heater in the room/basement to warm the place up. Commented Feb 17, 2015 at 21:53

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