Frozen Water Service Line

Question

Last Saturday, I returned from a trip and had no water flowing out of any faucet in the house. For context, the house is residential with water supplied by the city. My neighbors do have water. I had shut the water off while away but turned it back on upon returning home.

I had a plumber out, he removed the line just above my main shutoff valve. Valve worked fine. Looked inside the copper pipe (coming up out of the ground) but didn't see anything. He said the line must have froze underground and put heat tape on it. Today is Wednesday and I still don't have water. I've been trying to get another plumber out but haven't been able to yet.

I'm looking for advice on how to thaw the service line. I've been looking online and through forums but most advice has to do with plumbing that is accessible or inside walls, not underground. Has anybody had this problem before? Any recommendations on how to thaw the line? Options I've seen are this "arctic blaster" which blows steam into the line and melts the ice. The thing is, it takes weeks to ship and is very expensive ($1800). Other things I've considered are pouring boiling water down the line? Is that safe? I also read something about using a welder, but I'm not a professional and don't want to burn the house down. Not sure if there's another option?

I've kept my faucets open to relieve pressure, but the bigger question is whether the line will crack/has cracked underground and needs replacing. My thought is, get the water flowing first, see if the pressure is good (indicating no leaks), and if the pressure is poor, then look for a leak underground/crack in the copper service line.

The line is copper. We’ve had cold temperatures for an extended period. Single digits Fahrenheit for a few weeks.

I had the city come out and mark the line. Apparently the line is 2 ft deep but our frost line where I am is 3 ft. That’s why I believe it’s frozen.

Answer 1

Normal ways to access pipe melting in a timely manner are to call someone properly equipped - as I guess your first plumber was not.

The "welder method" requires access to both ends of the frozen line, which has to be metallic, and then running current through it to warm it up. No welding should take place, it's just using a portable welder as a source of heat. It's either a service your local portable welding service offers, or it's not. With a municipal supply you'd need their blessing (I have considerable experience of having a local welder do this for us, but only with wells, and none once we ran a new water line deep enough.) Done correctly no fire risk should be involved. Your water company may be able to suggest an approved welding service to perform the job, or tell you that's not an option on their system.

The other common method is a pump and a small diameter tube with a supply of warm-to-hot water, where the small tube is fed into the pipe and warm-to-hot water is pumped down the tube to melt the ice where it stops the tube. Then the tube is pushed in further until it's through the ice. The return water may be captured and reheated, or not. This is the method properly equipped plumbers use now in my area. Steam adds unnecessary hazards to the method for little gain. Your common method to access the tech in a timely manner is to hire a plumber who already has one, not buy a unit, but if you stay away from steam it's amenable to home-brew without excessive hazards.

Answer 2

I back fed a frozen cold water pipe with hot and it melted the ice and sorted it.

The system I have is mains pressure on both the hot and cold sides so there was no issue when the cold came through. You may have to consider what may happen if your system is different.