# Question About Frozen Pipes **URL:** \ **Category:** Factual Questions\ **Created:** [March 5, 2014, 4:12pm UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932 "2014-03-05T16:12:30Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![ethelbert](https://avatars.discourse-cdn.com/v4/letter/e/958977/32.png) [@ethelbert](https://boards.straightdope.com/u/ethelbert)\ **Post date:** [March 5, 2014, 4:12pm UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/1 "2014-03-05T16:12:30Z")
When water pipes freeze and burst it is most likely the hot water pipes (I don’t have a cite for this and I could be wrong). My understanding as to why this is so is that the toilet acts as a pressure release for the cold water pipes. When cold water pipes freeze, the water in the pipes can be pushed out into the toilet tank so that the ice will expand along the length of the pipe, rather than expand outward and break the pipe. If this is so, is there a faucet with a pressure release for the hot water? I would think that if such a device were installed in the sink furthest from the hot water heater it would greatly reduce the chances of burst pipes. ---
**Author:** ![Gbro](https://avatars.discourse-cdn.com/v4/letter/g/c6cbf5/32.png) [@Gbro](https://boards.straightdope.com/u/Gbro)\ **Post date:** [March 6, 2014, 1:31am UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/2 "2014-03-06T01:31:20Z")
I don’t know where a story like that came from. A toilet valve is a positive shut off valve. A cold water tap is probably used much more than the hot tap and that will be triple at night. I would say, if hot water pipes statistically freeze more often its because cold water is used more. Kind of reminds me of the old myth that when a fire engine is running during a fire the truck can pull the water out of toilets. :smack: ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 6, 2014, 2:12am UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/3 "2014-03-06T02:12:22Z")
water freezing would likely occur at cold spots and in layers, this would be local freezing and the idea of pressure relief would have no effect. the toilet tank valve holds against lots of pressure otherwise your toilet would always be running. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [March 13, 2014, 8:26pm UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/4 "2014-03-13T20:26:31Z")
I remembered this thread while reading [this article](http://www.nytimes.com/2014/01/09/garden/if-winter-takes-aim-at-the-pipes.html?ref=bobtedeschi) about frozen pipes. According to the interviewed expert, > [@](#): > > Ask a plumber whether hot or cold pipes burst more frequently, and they’ll all tell you it’s the hot water pipe… > > They’ll give you a whole bunch of different answers, but the real answer is the toilet. The guts of a standard toilet actually function as a pressure-relief device. If the water pressure rises in the pipes, the ball cock allows a drip of water to leak out into the tank. Hot water systems don’t have anything like that, so they’re more at risk. I don’t know if that’s true (there are a lot of old wives tales among plumbers) but I do not particularly want to test it, either. ---
**Author:** ![chiroptera](https://avatars.discourse-cdn.com/v4/letter/c/df705f/32.png) [@chiroptera](https://boards.straightdope.com/u/chiroptera)\ **Post date:** [March 13, 2014, 8:52pm UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/5 "2014-03-13T20:52:18Z")
[Hot water freezes faster](https://medium.com/the-physics-arxiv-blog/d8a2f611e853). Also (from someone who lives in a cold climate and has had her pipes freeze more than once) leaving faucets running, if you have vulnerable pipes, really works. The standard advice is to leave the hot water faucets running with a pencil-lead sized stream whenever it gets risky-cold. That relieve the pressure in the entire system, so the pipes don’t freeze all the way through. How it was described to me by the owner of a large plumbing company, anyway. And It’s worked, since even during the big ice storm where my house had no heat or electricity for six days, and icicles were coming out of every faucet…once it all thawed, no problem. I’d left all my faucets running as instructed. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [March 13, 2014, 9:15pm UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/6 "2014-03-13T21:15:20Z")
> [@chiroptera](#): > > [Hot water freezes faster](https://medium.com/the-physics-arxiv-blog/d8a2f611e853). No it doesn’t, at least not in any way that’s sufficiently reproduceable, and that article is full of speculative jibber jabber. ---
**Author:** ![chiroptera](https://avatars.discourse-cdn.com/v4/letter/c/df705f/32.png) [@chiroptera](https://boards.straightdope.com/u/chiroptera)\ **Post date:** [March 14, 2014, 12:44am UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/7 "2014-03-14T00:44:36Z")
> [@friedo](#): > > No it doesn’t, at least not in any way that’s sufficiently reproduceable, and that article is full of speculative jibber jabber. Cite to back up your claims, please? I’ve heard the “hot water lines freeze faster” for decades and every time I’ve googled it I find it reinforced. This last winter even my local water department was advertising that folks let the HOT, not the cold, water trickle since the hot froze up faster. But I am neither a physicist nor a chemist so I can’t evaluate such claims. But if you have a valid, understandable cite that claims cold water pipes actually freeze up faster than hot water pipes, and why I should ignore the advice of countless plumbing companies, municipalities, water departments and .edu sites, I am all ears, seriously. Since I live in a very cold-winter climate, and have a crawl space instead of a basement, I am personally invested in this. ---
**Author:** ![nevadaexile](https://avatars.discourse-cdn.com/v4/letter/n/eb8c5e/32.png) [@nevadaexile](https://boards.straightdope.com/u/nevadaexile)\ **Post date:** [March 14, 2014, 1:00am UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/8 "2014-03-14T01:00:53Z")
> [@chiroptera](#): > > [Hot water freezes faster](https://medium.com/the-physics-arxiv-blog/d8a2f611e853). > > Also (from someone who lives in a cold climate and has had her pipes freeze more than once) leaving faucets running, if you have vulnerable pipes, really works. The standard advice is to leave the hot water faucets running with a pencil-lead sized stream whenever it gets risky-cold. That relieve the pressure in the entire system, so the pipes don’t freeze all the way through. > > How it was described to me by the owner of a large plumbing company, anyway. And It’s worked, since even during the big ice storm where my house had no heat or electricity for six days, and icicles were coming out of every faucet…once it all thawed, no problem. I’d left all my faucets running as instructed. Actually, that would violate the laws of physics. Hot water molecules are more active than cold water molecules. That means that their motion would require greater energy to slow (and thus “cool”) them than would hot water. For an example of this, take a two pans of water, one boiling hot and one cool but still liquid, outside in subzero weather and throw them into the air. While they will both freeze in mid-air, the cold water will likely be already frozen in the pan before you get a chance to throw it. ---
**Author:** ![chiroptera](https://avatars.discourse-cdn.com/v4/letter/c/df705f/32.png) [@chiroptera](https://boards.straightdope.com/u/chiroptera)\ **Post date:** [March 14, 2014, 1:15am UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/9 "2014-03-14T01:15:56Z")
Again, cite? Look up the Mpemba effect. I has cites. Thousands more where the below came from. Please provide cites to counter this. Otherwise you are a random person online with an opinion, which is amusing but not authoritative. [http://math.ucr.edu/home/baez/physics/General/hot\_water.html](http://math.ucr.edu/home/baez/physics/General/hot_water.html) > [@](#): > > Hot water can in fact freeze faster than cold water for a wide range of experimental conditions. This phenomenon is extremely counterintuitive, and surprising even to most scientists, but it is in fact real. It has been seen and studied in numerous experiments. While this phenomenon has been known for centuries, and was described by Aristotle, Bacon, and Descartes [1—3], it was not introduced to the modern scientific community until 1969, by a Tanzanian high school pupil named Mpemba. Both the early scientific history of this effect, and the story of Mpemba’s rediscovery of it, are interesting in their own right — Mpemba’s story in particular providing a dramatic parable against making snap judgements about what is impossible. This is described separately below. > > The phenomenon that hot water may freeze faster than cold is often called the Mpemba effect. My neighbor and I TNR and feed a colony of feral cats. I’ve actually non-scientifically tested this theory by mixing up generic canned cat food with hot water and with cold water. For real, the canned food mixed with hot water freezes faster on extremely cold mornings. We mix canned food with cold water so it doesn’t freeze as quickly, because cats won’t eat frozen food. ---
**Author:** ![Habeed](https://avatars.discourse-cdn.com/v4/letter/h/a587f6/32.png) [@Habeed](https://boards.straightdope.com/u/Habeed)\ **Post date:** [March 14, 2014, 1:52am UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/10 "2014-03-14T01:52:35Z")
Valid possible explanations : 1. The hot water corrodes the inside of the pipes and causes wear more rapidly. I’m almost certain this is the reason : at my parent’s house, the same gauge of copper pipe was used for both the hot and cold sides of the system. The hot lines sprang dozens of leaks over time (apparently you are supposed to use a thicker gauge of copper for the hot side) 2. The pressure relief theory caused by toilet valves might be valid. It has absolutely nothing to do with “hot water freezes faster” because in water lines, the water is only hot when the circuit is in use (and it won’t freeze then). The rest of the time, the temperature in the hot line is the same as in the cold line. ---
**Author:** ![nevadaexile](https://avatars.discourse-cdn.com/v4/letter/n/eb8c5e/32.png) [@nevadaexile](https://boards.straightdope.com/u/nevadaexile)\ **Post date:** [March 14, 2014, 2:49am UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/11 "2014-03-14T02:49:06Z")
> [@chiroptera](#): > > Again, cite? Look up the Mpemba effect. > > I has cites. Thousands more where the below came from. Please provide cites to counter this. Otherwise you are a random person online with an opinion, which is amusing but not authoritative. > > [Can hot water freeze faster than cold water?](http://math.ucr.edu/home/baez/physics/General/hot_water.html) > > My neighbor and I TNR and feed a colony of feral cats. I’ve actually non-scientifically tested this theory by mixing up generic canned cat food with hot water and with cold water. For real, the canned food mixed with hot water freezes faster on extremely cold mornings. We mix canned food with cold water so it doesn’t freeze as quickly, because cats won’t eat frozen food. The Mpemba effect is not consistent: > **[A search for the Mpemba effect: When hot water freezes faster then cold water](http://arxiv.org/abs/1003.3185)** > > An explanation for why hot water will sometime freeze more rapidly than cold water is offered. Two specimens of water from the same source will often have different spontaneous freezing temperatures; that is, the temperature at which freezing begins.... [http://scitation.aip.org/content/aapt/journal/ajp/79/1/10.1119/1.3490015](http://scitation.aip.org/content/aapt/journal/ajp/79/1/10.1119/1.3490015) > **[On the Paradox of Chilling Water: Crossover Temperature in the Mpemba Effect](http://arxiv.org/abs/1101.2684)** > > Unlike most of the research on the Mpemba effect which has focused on verifying the observation that warm water freezes faster than cold water, our work quantitatively investigates the rates at which hot and cold water cool and the point at which hot... While under certain conditions IT could happen, it does not do so consistently. That lack of consistency makes it a speculative claim, not a scientific one. ---
**Author:** ![Habeed](https://avatars.discourse-cdn.com/v4/letter/h/a587f6/32.png) [@Habeed](https://boards.straightdope.com/u/Habeed)\ **Post date:** [March 14, 2014, 3:46am UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/12 "2014-03-14T03:46:07Z")
> [@nevadaexile](#): > > The Mpemba effect is not consistent: > > [[1003.3185] A search for the Mpemba effect: When hot water freezes faster then cold water](http://arxiv.org/abs/1003.3185) > [http://scitation.aip.org/content/aapt/journal/ajp/79/1/10.1119/1.3490015](http://scitation.aip.org/content/aapt/journal/ajp/79/1/10.1119/1.3490015) > [[1101.2684] On the Paradox of Chilling Water: Crossover Temperature in the Mpemba Effect](http://arxiv.org/abs/1101.2684) > > While under certain conditions IT could happen, it does not do so consistently. That lack of consistency makes it a speculative claim, not a scientific one. **Also,** the effect has to do with water vapor dispersing into clouds of gas more easily if it is hotter. It has absolutely no effect on liquid water in a pipe. ---
**Author:** ![bizerta](https://avatars.discourse-cdn.com/v4/letter/b/3be4f8/32.png) [@bizerta](https://boards.straightdope.com/u/bizerta)\ **Post date:** [March 14, 2014, 1:31pm UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/13 "2014-03-14T13:31:43Z")
> [@chiroptera](#): > > … The standard advice is to leave the hot water faucets running with a pencil-lead sized stream whenever it gets risky-cold. That relieve the pressure in the entire system, so the pipes don’t freeze all the way through. … It has nothing to do with relieving the pressure. Flowing water does not freeze. (OK it’ll freeze eventually, but it might take -80°C to get flowing water to freeze) If you leave a pencil-lead thin stream, the pipes may start to freeze, but eventually the opening would get small enough to make the water flow at sufficient speed to stop the complete freezing. ---
**Author:** ![Fool\_in\_the\_Rain](https://avatars.discourse-cdn.com/v4/letter/f/8491ac/32.png) [@Fool\_in\_the\_Rain](https://boards.straightdope.com/u/Fool_in_the_Rain)\ **Post date:** [March 14, 2014, 3:45pm UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/14 "2014-03-14T15:45:24Z")
> [@chiroptera](#): > > [Hot water freezes faster](https://medium.com/the-physics-arxiv-blog/d8a2f611e853). [The Master Speaks](http://www.straightdope.com/columns/read/422/which-freezes-faster-hot-water-or-cold-water) [QUOTE=Cecil Adams] Fascinating as all this no doubt is, all it basically proves is that very hot water freezes more slowly than very VERY hot water. The ordinary fumbler in the fridge, on the other hand, is dealing with temps more like the ones I was measuring, in which case cold freezes faster than hot. I rest my case. [/QUOTE] ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [March 14, 2014, 7:45pm UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/15 "2014-03-14T19:45:04Z")
> [@chiroptera](#): > > I’ve heard the “hot water lines freeze faster” for decades and every time I’ve googled it I find it reinforced. This last winter even my local water department was advertising that folks let the HOT, not the cold, water trickle since the hot froze up faster. But I am neither a physicist nor a chemist so I can’t evaluate such claims. Perhaps it’s a case of “one size fits all” advice. Here in NC, a lot of people have tankless water heaters, installed outside. Those people are advised to turn the hot water on at a trickle to avoid the pipes that are outside freezing. The pipes in the crawl space are at far less risk. I was glad I installed my tankless in my crawlspace. I don’t quite understand why people put them outside, but no doubt there’s a practical reason. (Luckily, my “crawl space” is about 9’ high, where the tank is. It’s 4’ on the other side of the house. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [March 14, 2014, 7:51pm UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/16 "2014-03-14T19:51:29Z")
I’m still thinking about the toilet-as-relief-valve theory. For one thing, I can test the sensitivity of the float valve to pressure. I’d open the cold water faucet in the sink, and flush the toilet. When the toilet stops, turn off the cold water and see if the toilet valve opens for a moment. If so, then I’ve established that it’s sensitive to pressure (which I don’t have a hard time believing.) The next question is whether that’s enough to do the trick. First of all, pressurized water has to be COLDER to freeze. So, relieving the pressure won’t stop the freezing, it would exacerbate it. Second, once the water is frozen, the pressure relief would be just at one end, and not rapid (ice doesn’t flow very fast). So, would that really be enough? Maybe. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 14, 2014, 8:11pm UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/17 "2014-03-14T20:11:36Z")
i lived in a place without central heat, manual heater in center room. the bathroom was a the rear. went away for a winter weekend; bath OK, sink OK, toilet froze. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [March 15, 2014, 12:05am UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/18 "2014-03-15T00:05:41Z")
The two or three times my pipes froze and burst, it was the cold water pipes which fed outdoor spigots. I forgot to turn off the water and drain the pipes over the winter. ---
**Author:** ![Spiderman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spiderman/32/230_2.png) [@Spiderman](https://boards.straightdope.com/u/Spiderman)\ **Post date:** [March 15, 2014, 3:32am UTC](https://boards.straightdope.com/t/question-about-frozen-pipes/682932/19 "2014-03-15T03:32:24Z")
> [@johnpost](#): > > i lived in a place without central heat, manual heater in center room. the bathroom was a the rear. went away for a winter weekend; bath OK, sink OK, toilet froze. No shit!