Frozen pipe: is the damage done?

February 2, 2011 10:09 AM

Frozen water pipe: call a plumber or wait it out? I've tried all the ehow-type articles I can find online, but the spot where my pipe is frozen is not very easy to get at.

I seem to have a frozen (but thankfully not burst) hot water pipe. The ice plug is only blocking hot water to the kitchen sink and dishwasher. I've had the cabinet below the sink open for about two hours now and have been warming the (copper) pipes with a hair drier. The pipes I can access are getting nice and hot, but unfortunately there are about 30 linear feet of pipe behind drywall in the basement between the last working faucet and the non-working ones, and the frozen spot could be anywhere along there. I have the hot water supply to the house turned off at the hot water heater and the kitchen faucet hot water left open, so I don't think I'm in danger of a burst pipe. I also kicked up the thermostat a couple degrees and fully opened all the vents in the basement.

So my question is: will a plumber be able to use any other tricks that I can't do myself (blowing compressed air through the line or something?), or should I just wait it out? Is the damage already done, or is there a chance it will get worse? Note that today's forecast high temp is 7F, but it should be in the 30s tomorrow and 40s on Friday. How long should it take to thaw the frozen spot?

posted by partylarry to Home & Garden (11 answers total)

Best answer: Turning off the water at the water heater and opening the faucet will not prevent a pipe from bursting. The pipes are already full of water. When water freezes, it expands. That's what bursts pipes.

As to the "30 linear feet of pipe behind drywall in the basement between the last working faucet and the non-working ones," it would help to know where these are routed. Is that drywall on exterior walls? Assuming the basement is at least somewhat heated, the only places that the pipes would be exposed to sub-freezing temps is where they run against / into outside walls or are somehow exposed to outside air.

Is this a full basement that extends under the kitchen sink and dishwasher, or do the pipes go out of the basement into a crawlspace or cantilevered section of the first floor before turning up into the wall / sink cab?

The plumber won't have any magic tricks (compressed air would be useless) but he might have better understanding than you do of where the pipes are, and where the frozen spot might be.
posted by jon1270 at 10:21 AM on February 2, 2011

Best answer: Frozen is frozen. If you can stand to wait it out until Friday, then do so. It won't get more frozen - any damage has already been done, when the water expanded as it froze.

If you really need the functionality of that sink, then call a plumber. They can thaw pipes with a blowtorch. (Kids: don't try this at home without a parent's supervision!)

My pipes freeze several times each winter. I find that it takes at least 12-24 hours of temps over 38 before the pipe thaws. This will vary depending on your microclimate, and the site of the pipe itself.

Note 1: if you call a plumber, they are probably hugely backed up, and might not even be able to get to you until Friday anyway. And they will charge you a fortune.

Note 2: Next time you get another batch of weather that cold, be sure to run those taps overnight. Just a small trickle of water will do the trick.
posted by ErikaB at 10:28 AM on February 2, 2011

They can thaw pipes with a blowtorch. (Kids: don't try this at home without a parent's supervision!)

For examples why you should be careful, google "frozen pipe"+"house fire".
posted by zamboni at 10:32 AM on February 2, 2011 [1 favorite]

Response by poster: Yes, these pipes are run along an exterior wall pretty much the entire run, but not through any crawl space--it is a full basement. If I recall correctly (from before the basement was finished), the pipes run along the top of the foundation walls, so they are actually above/behind the framing on those walls.
posted by partylarry at 10:36 AM on February 2, 2011

If you have or can acquire a couple of electric blankets you can potentially hang them on the wall in question to see if that would be enough additional radiant heat. And/or rent a construction-grade space heater to bring-up the room temperature if the area is isolated from where you spend your time.

That said, there's also the potential for a burst, which isn't leaking at the moment since it's frozen. Thawing it could be messy. Make sure you know where the shutoff valve is first.
posted by hungrysquirrels at 10:49 AM on February 2, 2011

Put a heat tape on that frozen pipe. When you can get at it, that is.
posted by Carol Anne at 10:52 AM on February 2, 2011

I would plan on calling a plumber whether the pipes burst or not. Behind drywall, along the top of the foundation walls, is a really dumb place to put water pipes for exactly this reason. They should be moved.
posted by jon1270 at 10:53 AM on February 2, 2011

Do you know how to shut off the water to that area? Sometimes, the freeze is not too bad, and the pipe warms up and is fine. Yay. Or, frozen water expanded, and pipe is damaged. Water pours out as soon as it thaws, causing flooding and other expensive damage. Warm up the area as much as you can. If you want, you can use a hair dryer to try spot warming. If you see/hear signs of water where it shouldn't be, cut off the water before the damage is horrible.
posted by theora55 at 11:20 AM on February 2, 2011

Response by poster: Thanks for all the responses so far. At least I feel better waiting it out for now, but I will see about getting those lines re-routed once the wait list for a plumber goes down a bit (I think last night was the coldest in Denver in >10 years). Unless of course I discover the pipe leaks once it thaws, then I'll have to get it addressed sooner rather than later. I agree that it seems like a pretty dumb spot for those water lines--I'm wishing I had them moved before getting the basement finished.

I don't have a shutoff valve for just that section, so I'm keeping the hot water supply to the entire house off for the time being, except to occasionally turn it on to check if the frozen spot has magically thawed, and I suppose I'll let Mrs. partylarry get a shower in at some point.
posted by partylarry at 11:41 AM on February 2, 2011

i am not a plumber, but i do have frozen pipes myself in one of our bathrooms. When this has happened in the past, i have opened all the cabinet doors below sinks and also where there is access to the tub plumbing. We cranked the gas wall heater and put ceramic heaters where they could warm under the sink. Stuffed a towel under the door so no heat could escape. We also turned the hot water faucets to on and left them until the water was running. This last bit was at the advice of a plumber. I thought it sounded like a diaster waiting to happen but it worked.

It hasn't worked yet this time, but it is only 17 degrees outside so that might be why. Atleast the wind is a tolerable 10-15 mph instead of teh 50 mph yesterday. It is currently so hot in my bathroom, I couldn't stay in there long enough to do my hair this morning.
posted by domino at 12:31 PM on February 2, 2011

Response by poster: Update: the frozen spot thawed after another 2 hours, and we appear to have avoided catastrophe for now. Thanks for all the input!
posted by partylarry at 4:45 PM on February 2, 2011 [1 favorite]