Dopers from the frozen north - how does city infrastructure work?

Factual Questions
1

Here in the UK the temperature rarely drops below freezing these days, but I sometimes see weather reports from the northern US and Canada talking of temperatures down to -30 or even -40 (ºC or ºF, take your pick) in the winter months.

Isn’t this cold enough for water mains, sewers etc to freeze up? How are utilities constructed in these really cold places to prevent this? I can’t see how standard buried pipes would be viable when the surrounding ground is frozen.

I know this is a fairly vague question, but I’d be interested to hear any info…

2

Even on the coldest days, the ground only freezes to a certain depth, which is known for each area. We simply make sure to put our pipes and foundations below that depth, and cover things up afterwards.

3

We still manage to get the anual water main breaks this time of year. I think it has more to do with the ground shifting and the pipes sliding than the pipes acually freezing though.
The pipes are run under ground (deeper than 6 feet) and brought into the buildings at the same grade so that any chance of freezing is eliminated. If any water source needs to be accessed from the surface (fire plugs, sprinklers, etc.) then there is a valve with a handle at the surface that extends a rod down to the valve buried below the frost line.
The queen of lubricants and others will be along shortly to give more info, but basically you had the right idea, bury it deep enough.

4

City piping is easy: It’s always full of running water so it stays above freezing. Country piping is a pain. Anecdote: My parents used to have a cottage north of Montreal. If they weren’t planning to stay up there in a winter, they’d drain the pipes in autumn. If they did intend to spend a substantial amount of time there in winter, they’d keep a little water running in the house at all times to keep the pipes from freezing.

5

We went through a record cold spell a few years back,way below zero several days in a row,-55 seems to stick in my head for some reason,tho I am not sure.Anyhow,the only thing I remember happening around town was that about one out of twenty cars would start,I was lucky enough to be one of those one.

6

I remember about 10 years ago we had a particulary long lasting cold spell. The pipes in many many homes froze and some burst. Constructions crews were very busy digging up the front lawns of house after house to repair the pipes.

7

As mentioned, pipes are generally buried deeply enough to prevent freezing. In addition, non-frost susceptible soil (NFS) may be used to bed the piping to limit heaving. This is also often used under building foundations and roads. Arctic engineering is a university discipline all its own.

8

I hope this was a typo. I don’t ever recall a day in michigan getting to -55 in the past few years.

9

Maybe with wind-chill factored in? (Of course, this would have nothing to do with the pipes belowground.)

10

Well, everyone else has pretty much covered it. Even up where I live, where -30 C is no big thing, pipes inside the city rarely freeze. The constant flow of non-frozen liquids (whether water or sewer) plus the depth of the pipes (which was about three meters deep on my old lot, and that was intalled 50 years ago) keeps everything moving. I’ve seen lots of pipes under trailers break if the skirting is done poorly though, which can be a real SOB to fix. This happened to my office early this winter when we got a pretty harsh cold snap. We just waited for the next chinook, and heat taped the lines, and it eventually cleared out.

More common are the storm drains freezing. This happens fairly often if we get a chinook coming of the mountains, which can raise the temperature 30 degrees in a day. Things start melting, and when the chinook ends, they freeze again. By the time the next chinook rolls around, there’s nowhere for the melt to go, leaving big slushy puddles. That’s when the city will send out steam trucks to clear the ice out of the system.

However, I’ve been told by the oldtimers that when things get really really cold (-45 C or colder before wind chill), it’s a good idea to have a tap in your home with a bare trickle of water running to make sure that it keeps running.

Of course, all of this only applies to the city’s infrastructure. Once you get outside of town, freezing is quite a bit more common. Heat tape will commonly be used to wrap pipes to prevent freezing, and usually people try to keep the majority of the pipes for their water tanks and septic systems under the house so the heat from the house will keep everything thawed.

11

I grew up in Fairbanks Alaska, and as everyone has said, the water mains are pretty well protected. But pipes in and to individual houses are at risk, everyone is paranoid about their pipes bursting. So people leave a trickle of water running, they insulate their pipes, they sometimes get electric heaters just for the pipes, they make sure not to just turn off the thermostat when they leave the house, and so forth.

And the ground is only frozen to a certain depth, even in areas of permafrost the permafrost only goes down to a certain depth. So you have an active layer on top that freezes and thaws annually, a layer of permafrost, and under the permafrost unfrozen ground. Of course, you can’t build on permafrost without special techiques, and even then you probably shouldn’t. There’s a famous sinkhole near the University of Alaska. Every year or every other year they used to add a new layer of asphalt to the sinkhole. Eventually they dug out 40 some feet of asphalt and tried putting down an insulation layer under the asphalt and radiators to keep everything cold even in summer. Didn’t work.

12

I’m a civil engineer here in New England.

Our standard specifications for water and sewer piping call for a minimum of 5.0 feet of cover, unless otherwise as on the plans or as directed by the Engineer.

Where the pipe is installed at less than the required cover, we require that the pipe be insulated with jacketed fiberglass insulation.

13

How do cities deal with situations involvling bridges and such? ie how do they get water to the other side of the river without worrying about those mains freezing?

14

Probably some form of heat tape. And electric wire that is wrapped abound the pipe under the insulation.

I use it in my house on the main incoming water line in an outside wall to prevent freezing. As well as on the roof to try to prevent ice dams that happen over the overhangs of the house.

Hard to explain. The overhangs of the house receive very little escaped heat from the house like the main roof does. Sometimes the heat escaping from the house will melt snow on the roof and as it runs down it will re-freeze at the edge of the roof. It forms a dam. Additional water running down from melting snow will build up this dam to the point that you have a large puddle of water on the roof. It’s a bit of a bitch. I’ve been fighting it for years.

15

boytyperanma Also, as others have said, the water is moving in these systems. It’s pretty hard to freeze moving water in a pipe in a short distance.

So, for a 4-5- or 10 inch main line that is hung on a bridge, it is probably not an issue at all.

The ground freeze and swell is more of an issue.

16

When I was stationed aboard a small ice breaking tug in Maine, this is precisely how we kept the exposed fresh water lines on the pier from freezing.

On a related note, we had one winter in Steep Falls, Maine, where the temperature dropped to -35 F. Our heating oil tank was outside, and the heating oil froze in the pipe leading into the house. After the heating oil company came out to thaw the pipe, we wrapped it in an electric baby bottle warmer which solved the problem. Well, that and kerosene.

17

Isn’t there such a thing as a “heat pump” that keep water mains from freezing?

18

We fight ice dams on the roof in two ways. We have a lot of insulation in the attic and also a fan to keep the attic the same temperature as the outside, so the snow on the roof never melts. Second, on some roofs you will see electric heating wires on the edges and they just melt the dams.

The only time I heard of pipes freezing was during the great ice storm of 1998. We were unheated for a week. We drained our radiators, drains, and water pipes and it didn’t get much below freezing until after our power, at least, was restored. A colleague of mine did all this, but it turned out that there was an old pipe inside his LR wall that did not drain since it was capped at the bottom. It froze, cracked, and then thawed when power was restored. What a mess!

19

A heat pump is another topic altogether. You’re probably thinking of a circulating pump.

20

Here in Minnesota, we often have cold weather in winter. The temperature just dropped below 0ºF (-18ºC), and is not expected to get back above zero until sometime Tuesday. Saturday is expected to be -29ºF(-34ºC).

Generally, pipes are buried deep enough (6 feet/2 meters) to avoid the problem. Or people will leave the water running a bit so it is moving in the pipes. (Increases your water bill, but that’s a lot cheaper than calling plumbers.)

Problems generally occur in small locations, where pipes happen to be exposed to the cold. Most of these have been found & fixed by people over the years. You will often find ‘tricks’ that you have to follow in an old house.

In my mothers house, if it’s extremely cold and the wind is from the northwest, the cold water pipe to the upstairs bathroom will freeze inside the wall where it runs by the front entry. To prevent this, she either leaves the cold water running a little bit, or goes down to the basement and makes sure the door to the unheated pantry storage room under the front entry is open.

Another example is an old farmhouse on our west farm. This old building has very poor insulation, and the kitchen sink water pipes are ok in the ground, they actually freeze where they come up in the back of the kitchen cabinets. So years ago, a heat tape was applied to those pipes, and wire comes up thru a small hole on the counter where it can be plugged into an outlet. Unplug that during a cold spell and you’ll have trouble.

So most of the time, people have come up with stop-gap solutions for their own buildings.

Underground pipes can also be helped by snow, which is an insulation for them. It’s not uncommon to see the water pipe into your house from the street water main freeze right under the shoveled sidewalk. (But that can be fixed without digging up the yard. You call a welding company, they come with a portable welder on a truck, remove your water meter and clamp one wire to that, the other goes to the nearest fire hydrant. Apply current for about 10-20 minutes and it’s thawed.)

Often, underground pipes will freeze not in the coldest weather, but in the spring as things are thawing. What happens is that the ice/snow melts during a sunny day, and the water flows downward, deeper into the ground. Then at night it gets colder, and that water freezes. This is referred to as ‘frost moving deeper’, and can freeze pipes unexpectedly.