Will my water filled pipe freeze?

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Discussion Overview

The discussion revolves around the potential for water in a fire sprinkler pipe to freeze under specific temperature conditions. Participants explore the implications of ambient temperature, insulation, and the role of latent heat in the freezing process, with a focus on whether antifreeze is necessary for the system's safety.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant describes the scenario of water pipes exposed to -8.5°C for 8 hours, starting from 6°C, and seeks a calculation to determine if freezing will occur.
  • Another participant questions the purpose of the water and the assumptions made about temperature, suggesting that the water may not reach 6°C during the day if it does not cool sufficiently at night.
  • A later reply emphasizes the importance of proper antifreeze use in fire sprinkler systems, warning against the risks of climate variability affecting system performance.
  • Some participants express skepticism about the assumption that the water will warm to ambient temperature, arguing that it may remain closer to -1.25°C, which could lead to freezing.
  • Concerns are raised about relying on latent heat as a safety factor, with participants suggesting that this approach is inadequate for ensuring the system's reliability.
  • One participant shares personal experiences of freezing pipes, emphasizing that static air conditions do not guarantee safety and that insulation or heat tracing may be necessary.
  • Another participant agrees that relying on latent heat is not a safe strategy and asserts that freezing is likely to occur under the discussed conditions.
  • There is a suggestion that the time lag for the pipe temperature to respond to ambient conditions may be minimal, indicating a risk of freezing.

Areas of Agreement / Disagreement

Participants express a range of views, with some agreeing on the inadequacy of relying on latent heat for safety, while others question the assumptions made about temperature changes and the necessity of antifreeze. The discussion remains unresolved regarding the best approach to prevent freezing.

Contextual Notes

Participants highlight limitations in assumptions about temperature fluctuations, insulation requirements, and the reliability of static air conditions. There is no consensus on the adequacy of the proposed safety measures.

engineroom
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I have a problem that my technical engineer training can't solve.

We have static water pipes installed under a canopy of a building. The coldest air tempreture recorded is -8.5 Celius during winter. We can assume that the air tempreture stays at -8.5 Celius and there is minimal air movement. If we assume that the pipe and water starts at 6 Celius and is exposed to -8.5 Celius for 8 hours will the water in the pipe freeze?

The pipe is 32mm OD, 25mm ID. The pipe is carbon steel.

Part of the answer is a formula for a curve that relates heat loss and time to tempreture. The differcult problem becomes when the tempreture reachs zero then the latent heat starts to be given up.

Currently me and the building inspector are having an argument as to whether the pipe should be dosed with antifreeze. I need a copy of the calculation to show the inspector.

Thanks for any help.
 
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What is the water for? (It seems the only factor for deciding on antifreeze should be whether it all recirculates.) Why "6" Celsius? It does seem a valid question (how much insulation does a pipe require?), although if you get to the point where latent heat matters, then you're outside of the building safety margin.
 
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cesiumfrog said:
What is the water for? (It seems the only factor for deciding on antifreeze should be whether it all recirculates.) Why "6" Celsius? It does seem a valid question (how much insulation does a pipe require?), although if you get to the point where latent heat matters, then you're outside of the building safety margin.


The water is in a fire sprinkler pipe. From climatic data expect worst case a high during the day of 6 celsius followed by an over night frost of -8.5 celsius. Even if the point where latent heat is factored in that is still okay, so long as we don't have solid ice.

Thanks.
 
Fire sprinkler? Just make sure the antifreeze is dissolved in properly, you'd be very silly to build an emergency system that doesn't work properly (or fails permanently) if the climate changes a little.

I don't like the way you've approached your climatic data. Why do you assume the water will warm completely (to the ambient 6 degree temperature) during the day, and not assume it will cool to ambient temperature at night? If it doesn't have time to cool to ambient temperature at night, it can't have time to warm up to the maximum during the day, so it will be at about the average -1.25 celsius all week, which is completely useless (it would freeze solid). You also assumed minimal air movement, which cannot be relied upon (imagine there is a cold front moving through): you should assume the outside surface will be the same as ambient temperature. Provided your pipes aren't physically connected to anything acting like a big heatsink, you'd want enough insulation that it only cools a few degrees over the worst week, in other words you'd want the above-ground pipes to be indoors.

I'd expect the building inspectors know something about safety, why are you so unwilling to follow that advice? How significantly does it alter the cost?
 
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It's going to freeze. At the least it will cause you troubles. I have seen people have problems with water pipes in homes where the water is moving and the pipes still freeze. Are these pipes out in the open or are they in an enclosed area such as an eaves area or the like?

Whether the air is static or not really doesn't matter. You're only going from 6C to -8.5 for 8 hours and it's a 1" pipe.

I fully agree that if you are relying on the latent heat as your safety factor, you are not being safe enough. That system has to work whenever and every time. You need to insulate or run heat tracing down the pipes to ensure free flow.

Where are you located? Don't they have specific code requirements for this?
 
Last edited:
FredGarvin said:
I fully agree that if you are relying on the latent heat as your safety factor, you are not being safe enough.
I fully agree. Moreover when the latent heat begins to "help", it is too late: water is freezing.
 
Right - that isn't safety factor you're talking about. It is already into failure.

If I had to guess, I'd say you will only lag the ambient temperature by an hour or two with a pipe size like that.
 

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