Hot Topics: Underground Frozen Pipes

A close-up of frozen grass and ground.

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Original Post: Pipes Frozen Underground

marksr Forum Topic Moderation

We've had an unusually long cold spell. It was below freezing for eight days. Either my water supply line or somewhere at the road froze up Saturday night. It's been above freezing since noon yesterday. Some of my PVC is only covered by 4" and I suspect it's one of those areas that is froze up. Any idea of how long it will take to thaw out? Today was in the low 50s.

aka pedro Member

In my experience, once the ground is cold it probably takes at least twice as long to thaw as it did to freeze. And I assume your overnight lows are still below freezing, so you're looking at 50/50 or something like that in any 24-hour period. Do you have snow cover? If so, and if your forecast is for warmer days, it might be worthwhile to scrape the snow off the line if you know where it is, but I'm thinking you might have too long a run for that to be practical. I've never had it done myself, as our water line is down about five feet, and I've never been there to see it done, but I know that they use a steam cleaner sometimes around here to thaw frozen lines.

Norm201 Member

It surprises me that you would only have 4" covered. The frost must be lower than that. I agree with AKA. The ground takes awhile to give up its heat and freeze, but once it does it's rock hard and takes as long to thaw.

Pilot Dane Group Moderator

Where I am in NC, water lines must be at least 12". But that doesn't mean all are that deep the whole way. There are a lot of things that aren't done properly to code.

I had a couple supply lines freeze on my rental properties. The meters aren't far underground and they are only protected by a cast iron cap/hatch. Without snow cover, the cold gets to them surprisingly well. A turkey fryer or very large pot of water on an outdoor propane burner can heat a usable amount of water for thawing. It doesn't have to be boiling. 120-140°F is enough to thaw out a meter and piping inside.

If you think the line in the ground is frozen, do you have a good idea where the problem lies? If you are expecting temps below freezing at night, anything you can do to insulate the area will help. Straw, old blankets, sheets of cardboard, or carpet over the area at night can prevent the freezing from getting worse. Then, remove the insulation before you go to work in the morning so the heat of the day, and especially the sun, can hit the area.

Bud9051 Member

I would suspect the pipe at the road is deeper than everywhere else, so those shallow spots are more likely. If you know where they are covering, at least those places at night would be good. The ground below is trying to warm the surface and losing that heat to the air. Covered and/or insulated will help. Hay or straw bales are often used up here.

marksr Forum Topic Moderation

Our frost line is at 12" and while most of my supply line is close to or deeper than that depth, there are several areas where it comes up the hill that blue slate made it next to impossible to bury the line. I've worked at building up the dirt/slate at those areas. Except for the blizzard of '93, it's worked well. What I did then was cut the line in a few places and force the ice out, but I've been fighting a cold for the last four to five days so that isn't really an option.

My son has a place at the bottom of the hill across the road and his water froze up two days before mine. We are convinced that freeze isn't under his house or meter, but somewhere between the road and the meter. I don't know if he ever got water, as he drives a truck and went back out.

It hasn't been below freezing since Monday morning. The current temp is 40 degrees with 55 being the expected high for the day. It's not expected to get below freezing again until this weekend.

Bud9051 Member

Pedro asked about snow, and at those temps I assume you have none. If you know exactly where those trouble spots are, I would stretch out a length of heat tape (they have a safe style that's self-regulating) and cover it with some rigid insulation and tarp at night. Daytime warm weather will make progress and the insulation plus heat will continue through the night. My guess is one night and you should be free.

core Member

Insulation and heat tape and similar approaches all sound like a lot of effort, especially when one is not feeling well. I would just toss some wood on all the low spots, sprinkle with a little diesel or kerosene, wait for it to soak in, and then light all the piles.

Vermont Member

When we don't have a sufficient insulating snow cover, we arrange bales of hay above the known trouble spots to provide some insulation.

What's really bad is when we have a lot of snow in December followed by a "January thaw," which melts all of the snow, and then we immediately go into -30°F or -40 °F to put our water lines inside a solid subterranean block of ice. There's little that can be done to protect against that.

marksr Forum Topic Moderation

Anything that requires electricity isn't really an option. The closest pipe that could be frozen is at least a couple hundred feet from an outlet. Most of these areas are on a 45° or steeper angle. Hopefully, today's temps will thaw it out! A hot shower would be nice!

Pilot Dane Group Moderator

It doesn't help you now, but whenever you have bad cold snap, you'll need to get in the habit of leaving some water running to keep the water in the line moving so it doesn't freeze. If you are on a septic system, you may consider some way to run water without putting it into your septic. No sense in having the load on the system if you don't need to.

marksr Forum Topic Moderation

I leave a tap running whenever it gets into the single digits, but the water pressure dropped. Saturday afternoon there was just a drizzle, but shortly after dark we had decent water pressure for a short while and then nothing. It isn't uncommon for us to loose water pressure when they work on the lines elsewhere.

I did make it down to the meter a little while ago and it wasn't moving. I would have thought that being in the 60s most of the day, I'd at least get a trickle up to. I know it doesn't help that the water line is on the north side of the hill.

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