Shallow well-"It never freezes in the pit"


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Old 10-17-18, 09:03 AM
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Shallow well-"It never freezes in the pit"

My first vacation cottage had a shallow well with the pump located in a hand-dug pit 8 feet deep (8x8x8 pump pit). When we bought the place I was told there's no need to winterize the pump because it sat below the frost line. So I never did, and I never had a problem (5 years).
BUT I still don't understand why if heat rises and cold air falls why doesn't the pit fill with ambient air and freeze? This is on the 45th parallel and winter temps get into the negative double digits on occasion.

Bad advice but dumb luck?
 
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Old 10-17-18, 09:19 AM
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The earth holds heat along with the fact that the pit is protected from the wind which slows down any heat loss. It may never freeze but I'd be inclined to take some precautions.
 
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Old 10-17-18, 11:15 AM
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Even in the coldest or winters your basement (assuming it is not a walk out) will stay around 50-55 degrees, it's the natural temp of the earth when you get below the frost line!
 
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Old 10-17-18, 11:19 AM
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I would agree; but you should do what you can to block or inhibit the air exchange with the ambient temperatures above grade.
 
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Old 10-17-18, 06:05 PM
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Well, it's the same reason that even small ponds don't freeze solid, The summer heat and winter cold move as pulses downward through the earth, but after a few feet, the rock and soil stay at average air temperature.


https://www.builditsolar.com/Project...mperatures.htm

See also https://www.weather.gov/ncrfc/LMI_So...atureDepthMaps

As for water freezing, we all know that cold water sinks and hot water rises.
But, we're wrong.
Below 40 degrees F. cold water rises.
Basically, ice floats, below 40 degrees, liquid water starts acting a little bit like ice, and it starts to float.
The result of this is that cold water rises, it gets colder, so it rises more, and you end up with an insulating layer of ice on the water surface. It takes LOTS of heat to convert water to ice, which is why ice is so good at cooling, but ALSO why water is so good at not freezing solid.
 
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Old 10-17-18, 11:34 PM
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It takes LOTS of heat to convert water to ice,
Should this say lots of "energy" to convert water to ice?
 
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Old 10-18-18, 03:35 AM
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Yes, should have been better phrased, should have been
"liquid water stores lots of heat, so something has to take away LOTS of heat to convert water to ice"

I did intend to say heat, actually, the term is "latent heat"-



So, if you try to cool water from a 60-degree liquid to a 0-degree block of ice,
fully HALF of the energy change (heat) goes into freezing.


Basically, the water in the sump pump is the "terminal" of a heat battery.
It charges the ground with summer heat, then drains as that heat flows to negate winter cold.
The 40-50 degree deep soil temperature is like a trickle-charger, it slowly replenishes the heat.
 

Last edited by Hal_S; 10-18-18 at 04:20 AM.
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Old 10-18-18, 04:33 AM
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Better explanation.

The water in the well (and the groundwater it is connected to) holds a lot of heat,
The air in the basement doesn't hold or carry much heat.
The basement air can't remove heat fast enough to create ice.

Quick estimate,
https://physics.stackexchange.com/qu...ption-capacity
Consider the volume of air in the basement, then consider an equal volume of water (water in the well and groundwater thermally connected to the well). The total heat stored in the shallow groundwater and well is about 3,000 times greater than the total heat stored in the basement air.

There's lots of total heat stored in the groundwater, but little capacity for the basement air to remove it. The basement air is a thermal bottleneck,

Let's try dropping the groundwater temp from 45 (average) to 32 (freezing)...
That requires removing 13 degrees of heat from the water; s imagine air that's 13 degrees below freezing, to move that much heat via basement air, we'd need to exchange all the basement air about 3,000 times to carry away all the heat in the water.

Then you would START to get ice.
 

Last edited by Hal_S; 10-18-18 at 07:16 AM.
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Old 10-18-18, 07:05 AM
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Sounds like you're saying it's very unlikely that a well pump in a basement could freeze--but it did happen to me. I never had a problem with cottage #1 with the pump in a small 8-foot deep ground pit, but cottage #2 has the pump in a basement utility room 8 feet under grade and in February 2015 during a particularly cold spell my boiler quit (bird stuck in the damper) for a couple weeks and my pump and many feet of copper pipe in the crawlspace burst.

I think the pump is too far away from the well to get much benefit from the "warm" ground. And the walls? I guess they just lost the battle with the ambient air.

This is why I've never really understood why I had no problem in a small ventilated pit but my larger basement room froze.
 
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Old 10-18-18, 08:16 AM
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Originally Posted by guy48065
This is why I've never really understood why I had no problem in a small ventilated pit but my larger basement room froze.
Eh, "sweater effect"
Sweaters and insulation work by trapping the air that you've warmed,
preventing air from of rising, and keeping it around you.

Big open basement - lots of air convection available to remove heat.
Small pump pit - less air available.
 
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Old 10-22-18, 07:41 AM
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Should this say lots of "energy" to convert water to ice?
It takes 70 times the energy to change 0 degree Celsius ice to 0 degree Celsius water, then it does to change 0 degree water to 1 degree water.

As mentioned that is why it is actually fairly difficult to freeze water but once you do it is then quite difficult to change it back. It's why it takes almost no energy at all for those little pipe heaters to keep water from freezing in your pipes.
 
 

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