I could not find my old thread so here we go again. I think I have an idea that will help me keep a water main, that I cannot bury deep enouph, from freezing. I the area where the line comes close to the surface I am going to wrap it in reflectix, maybe 2 layers, then backfill over the top as much as I can, probably 12″ of fill dirt. The reflectix should provide R-8. Comments?
HC
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No, If yours in the one through the woods for vacation house.
NOT AMOUNT OF INSULATION WILL KEEP SOMETHING FROM FREEZING.
What is does is slow down the rate of heat transfer.
Take two jugs of water and place it outside during the winter, but one in an insulated box. The first might freeze in a couple of hours while the other one might take a day or two. BUT IT WILL FREEZE.'
You need a heat source to keep it from freezing. Now one source is flowing water. But there won't be any if the house is not in use.
Another source from the earth. If it is burried deep enough then soil above it acts as insulation, but the warm earth under it.
If you wrap the pipe in insulation you are BLOCKING heat from he earth.
Why do you think the earth will warm it? I think you have to go down quite a ways before geothermal heating becomes detectable. I have a similar problem - ledge, etc. I made a suggestion about heat tapes but Piffin was skeptical.
"Warm" is a relative term here.You don't have to go that deep before there is enough heat to keep it from freezing. 6" to 4ft in most of the US.Now where Dave is in Alaska it is much deeper.
I have rock at the surface in a few spots and it straddles a property line, and goes through a forested area that I am trying to preserve(big trees). If it were not such a tight squeeze I would just back a dump truck up and cover with a tractor. If I can't find a solution then I'll have to pull out the chansaw and blaze a path for a tractor. I can wheel barrow some backfill in but I have limits.
Thanks everyone for trying to help.
HC
I'm sorry, Bill -- but I don't believe this "heat from the earth" business. The water comes out of the well at, say 45F. The goal is to keep it from freezing when it comes into contact with soil at, say 20F. Insulation should help keep the heat of the relatively warm water in the water, rather than being lost by conduction to the cold soil. Your model is just the opposite -- you envision heat entering the cold water from the relatively warm soil, and so insulation (because it would prevent this) is a bad idea. I don't think we can both be right on this one. Too bad it's not just a theoretical question.
I'll help you out. Both of you are not right, Hartman is right.
Soil temps are usually in the 50's around here (outside boston). In the winter, the temps will be as low as -10 to -15 and the ground will freeze. If we have snow on the ground early in the winter, then the cold air temps will not penetrate the ground because the snow acts an insulation. If we don't have snow and the temps drop to below zero or even in the teen's, the cold will penetrate the ground but only to a certain point. The deepest the frost gets around here is a max of 3' but usually much more like 1 to 2 feet. The earth does have a natural temperature that is relatively warm compared with the cold winter.
I don't know where you live but when you dig in the winter, the fozen soil will look like chocolate but once your down below that it is perfectly loose soil.
The only soil at 20F is the frost layer at the surface. The frost will penetrate at different levels depending on snow and the temps but never does it go down to 5ft where the water lines are.
Edited 4/19/2005 9:35 am ET by DDay
OK, I now agree with Bill (and I like his water bottle thought experiment), with the qualification that I think the source of heat is the moving water and not the earth. Not to quibble, but it isn't really that the cold penetrates, it is that the heat leaves. Conduction moves heat from relatively warm things (the soil, in winter) to relatively cold things (the atmosphere, in winter). Snow keeps the heat in, not the cold out. (OK, I am quibbling!)
I'm in Vinalhaven, ME, where the soil froze to a depth of 10 feet last winter, so this is a biggie for us.
Soil frozen 10 feet deep? Wow!One thing I noticed on Vinal and North Haven last summer is the huge number of horizontally mounted oil tanks - mounted on concrete pads outside houses. do you guys run Kerosene? Also, how do keep the water flowing - indoor wells?
The ground keeps the pipe from freezing because it's storing a large amound of heat - not because it's generating heat. Obviously, there is a lot of thermal mass in the ground, so in order for the ground to freeze, it has to get very cold for a significant period of time. The colder and longer, the deeper the freeze will be. In most areas of the US, the heat in Summertime warms the soil back up and stores the summer heat until winter rolls around again, and the cycle repeats.
Way up north in parts of Alaska, Siberia, etc., the summer is too short and too cold to warm the earth and completely shake off the winter freeze. In these areas you have perma-frost - which means the ground is always frozen at a certain depth. In the summer, the top foot or two may melt, but there is never enough energy to completely thaw the ground, like there is here in the lower 48.
In essence, there is a ratio of summer energy transfer to the soil vs. winter energy loss pulling heat from the soil. The further north you go, the more the ratio favors heat loss, and after a certain point, the loss outweighs the gain and you have permafrost. The more south you go, the opposite is true - I'm in central Florida and we never have to worry about the ground freezing.
Hope that explains things a little bit.
Yes, those are kerosene tanks to supply Monitor heaters -- a very popular choice. We spend summers on Vinalhaven but plan to live there year-round soon, so this is a serious concern. The well heads are generally quite a distance from the house -- 50 ft to several hundred ft., depending on where the drill rig got to. Year rounders reported the 10 ft figure, and I have no reason to doubt it except that the year rounders like to regale the summer people with stories about how the horrible the winter was. We spend winters in Buffalo, NY, so I'm not as impressed as some people.
A) have you ever been in a cave?B) it does not matter what the temp is coming out of the well, it could be 200 degrees. If the water is NOT FLOWING then it will cool off and freeze if the OT is below 32.I will repeat what I had in my first message.Take a two jugs of water and set them outside in freezing weather. You can put as much water as you want around on of them. They are both going to loose heat. It is just that the one that insulated takes longer. It may take a day or two to freeze, but it will freeze.INSULATION DOES NOT STOP THE FLOW OF HEAT, ONLY SLOWS IT.You need a source of heat to keep the pipe from freezing. That source can be the earth, heat tape, or MOVING WATER. But when the water stops moving you source of heat stops.
Won't work.
Reflective insulations only work for radiative heat, such as from the sun. Here you have the dirt piled onto the stuff, so thermal conductivity will enter in. Most of these are only a fraction of an inch thick, so you will have essentially zero insulation.
Secondly, even with insulation, where will you get the heat to keep the pipes warm? You would have to regularly run water down the drain to warm the pipe.
If you REALLY have this problem, get some foam insulation like that used on the outside of foundations. AND get some self-regulating heating tape like that used on gutters. Put the tape on the pipe, and plug it in.
NOTE: You MUST use the self-regulating type of heating tape, which cannot overheat.
As Hartman and JohnD said, no heat the pipe will freeze.
There is a type of heat tape that goes INSIDE the pipe. It's made by Tyco Thermal and is called Wintergard. Of course, if the power goes out or if the heat tape gives up the ship, your water line will still freeze. The advantage of this stuff over the regular heat tape that goes on the outside of the pipe is you can replace it without digging the pipe up.
http://www.tycothermal.com/usa/english/heattracing/applications/residential/pipefreeze/default.aspx
maybe I should cover with reflectix but not wrap so heat from ground is trapped, then backfill 12" or so over it. Gotta wheel barrow it in, fun
HC
Here we often use a PYrotenax heating cable inside the pipe when we cannot dig down at least 3' in the soil . If the building is in use we put some sand then 1 1/2 styrofoam 2' wide and backfill with sand then reguler fill .