Wind chill and water pipes

Tonight in NYS supposed to be 0F, and wind chill -10 or so. Which number is the one which concerns water pipes freezing?

I know the pipes won't get below the actual temp, but are they more likely to freeze, with wind?

Reply to
Stormin Mormon
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We went through that just a few days ago on the other thread.

Wind chill below freezing will /not/ freeze the pipes

Just as long as the temp. is above 32F they will be fine

Reply to
philo 

But wind can be a component of making it easier for pipes to freeze that are in certain locations, like an exterior wall, a crawl space that has some drafts flowing through it, etc. The same pipe that might not freeze at 15F on a calm night, could freeze on a night with a 20 mph wind.

Reply to
trader4

You may wish to read my post (above) again, and rewrite your comment in this thread, based on tonight's expected temps.

What you say is true, but it's not really relevant, tonight.

Reply to
Stormin Mormon

Yep I totally missed "OF" It just plain did not register.

trader4 is quite right

if the pipes are in an uninsulated and not well sealed wall, the more wind there is the more likely it will get in to cool things off

Reply to
philo 

" snipped-for-privacy@optonline.net" wrote in news:e7fc558c- snipped-for-privacy@googlegroups.com:

That's the correct answer. It all depends on

1) exposure to wind; 2) heat emitted by surrounding walls, machinery, etc.; 3) length of time subjected to the low temperature; 4) diameter of the pipe; 5) amount of water-flow though the pipes; and probably other factors I haven't thought of yet.
Reply to
Tegger

Ah, well. I have my moments of miss things. Anyhow, tonight is the one night of the year I'll be certain to leave a faucet dripping at the farthest place from where the water comes in. Help to avoid frozen pipe, if possible. My line from the curb valve is soft copper, and will not survive a freeze cycle. The lead in line is insulated, and heat taped. Not sure how good are the lines under the trailer. I think they go along the heat run, but not sure.

Reply to
Stormin Mormon

Wind chill is the effect the combination of cold air and wind has on exposed flesh relative to only cold air. "Wind chill" has absolutely no effect on inanimate objects. The wind on an inanimate object will cool an inanimate object to the ambient temperature quicker than no wind. It is impossible to get an inanimate object colder than ambient temperature by using wind that is also ambient temperature.

Now, don't ever ask that question again or I'll turn this car around...

Reply to
Gordon Shumway

Yep I'd leave the water running a bit for sure.

Reply to
philo 

That's absolutely correct but trader4 made a valid point.

Air in a wall would be warmed by the house and if no outside air got in would act to keep the pipe warm. With a strong wind blowing, any warm air trapped in the wall would be dissipated pretty fast.

Reply to
philo 

Which of course means that wind chill does have an effect on inanimate objects, in some cases. If you take an inanimate object like a brick that's at 70F and put it outside where it's exposed when the wind chill is 0F it's going to cool off faster than if you put it outside when the wind chill is 15F, even if the actual temperature in both cases is 20F. Once it's reached 20F, then it will have no further effect of any significance.

In the case of freezing pipes, I would say in many cases wind chill does matter, because any place that is drafty, or even an exterior wall, is going to be effected by the wind. The pipe in the wall could be colder on a night with a lower wind chill, even though the actual outside temp is the same.

It is impossible to get an inanimate object colder than ambient

Reply to
trader4

What I said is completely true, period. What the temperature in the wall that contains the plumbing is, or will become, whether it's insulated well or not at all, is the ambient temperature, period.

Granted, plumbing in an outside wall that is poorly insulated will have a greater chance of freezing at a given outside temperature when it's windy than not but that's what was contained in my statement.

Damn it, I WILL turn this car around! I'm not kidding.

Reply to
Gordon Shumway

No, no, no.

Yes, but the ambient temp in your example, is 20F. Wind chill does not have time in its' calculation.

You would be wrong. If it is going to freeze it may do it sooner but the pipe will not get colder than the ambient. Period.

Reply to
Gordon Shumway

Both. If the wind can get to the pipes, they will freeze faster with a wind chill of -10F than a temperature of 0F with no wind. If the wind can't get at the pipes, wind-chill doesn't matter.

Reply to
krw

But if you're smart, you move someplace better than where it stays below 0F for days, or weeks, on end. It'll be cold here next week, too. The highs will be in the 30s next week (but back to 60 for the weekend).

Reply to
krw

If they are exposed to the wind they will cool faster - but the wind will not drop them below the actual ambient temperature.

Reply to
clare

At 0F they will freeze regardless

Reply to
clare

My brother has his trailer fully skirted, and the skirt insulated to minimum R15. The space under the trailer is heated. (pipe from outdoor wood furnace runs length of the trailer to the heat exchanger in the old propane furnace) It was -35 last week, expecting -40 or better.

Reply to
clare

Just don't do 100mph in a 60mph zone. Remember - it will be ZERO F - not ZERO C.

If the ambient temperature gets to the pipes they WILL freeze.

Reply to
clare

This is a simple thermodynamic process of heat flowing from hot to cold. Wind Chill is a SINGLE number that estimates the effect of wind in ONE particular instance related to typical human behavior...nothing more...it's useless for predicting different situations.

Freezing pipes is a VERY complex problem involving many unspecified variables in the plumbing and structure. And it's not steady state.

The ONLY way to guarantee your pipes won't freeze is to keep the coldest spot above freezing. If you have a very good model of the system, you can use insulation and thermal mass to increase the time to freeze to longer than the below-freezing event.

Beyond that, you have to supply energy. Heat the structure and let some of it leak into the vicinity of the pipes to keep the temperature above freezing. Heat tape directly on the pipes.

Higher temperature water flowing thru the pipes at a rate sufficient to supply more energy than is lost thru the pipes to the cold environment. This is particularly helpful when your system is basically warm, but the pipe passes thru a short uninsulated region. I had a pipe burst in a rental because the idiots ran the pipe right across the attic vent then down to the washer.

A boundary layer forms at the interface providing a small amount of insulation. Air flow can destroy this layer and increase the rate at which heat is lost from a hot pipe into a cold environment. If the wind is howling outside and the pipe is in the middle of the insulated space, the wind is irrelevant...for constant temperatures.

So, what you care about is wind speed and how much of that actually affects the pipes in your exact configuration.

The wind chill number on the TV screen is related to the effect, but misses most of the variables for pipes. You can say that lower wind chill number is worse, but you can't say much about how much worse.

Reply to
mike

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