dry ice to stop a leak

Someone told me you can use dry ice to freeze a leaking pipe if there is no shut off so that you can then make repairs. They added that there is something you can buy that does the same thing but uses gas to freeze the pipe. I'd never heard of this. Can someone expand on it plz?

The one requirement for ANY freezing to be successful is that you have to be able to stop ALL flow of water through the pipe, otherwise the water will keep thawing it before it completely closes the pipe. One problem is to know when the freezing has been successful, because if you open a faucet to see if the flow has stopped and it is not frozen, you will thaw the blockade and have to start over.The commercial versions use "liquid co2" to freeze it faster. In some cases you use two "bags", one on either side of the area to be repaired.

What if you need to solder the line? Could you freeze the pipe far enough away from the broken line so that the torch wouldn't melt the blockage ?

It would only work well IF you froze it at least some way away from where you were going to solder; otherwise, you'd get some drips that would cause your solder joint to fail.

There are other devices that can work under some circumstances, like the JetSwet (sp?). If you are installing a full-port ball valve, and only have a trickle left, you insert the JetSwet into the pipe, tighten it down, side the new valve in over the handle, solder it in place, then pull the Jet-Swet out.

http://brenelle.com/

You could try a JET SWET if you have a valve that does not hold. You may have to shut the water off at the main shut off, or the water meter or a backflow preventor if you are in a municipal building. If you have your own private well, turn the power off to the pump and let the pressure drain from a faucet. If you have a sweat copper line, I'm betting the hole is close to where a fitting has been soldered on. If you feel you are in over your head you can get a hose clamp and a piece of rubber and tighten the clamp down on the rubber over the hole to at least isolate the problem and stop the mess until you form a plan to do the repair. I work at a university and this kind of on the fly repair is done very often. Shutting a building down where research is taking place is a big deal. Somewhere, there is some way to turn off the pressure. The above link is to the Jet Swet site.

Dry ice is probably not enough, because you need a constantly refreshing source of cold...liquid CO2 or Liquid Nitrogen.

Freezing is done all the time in industrial applications at pressures you don't even want to think about. They freeze as far as practical from the joint to be welded, but can actually work farily close to a good freeze. google "cold-shot" for a CO2 system, and "jet swet" for the system which uses expansion rubber plugs.

Dry ice CAN do the job if you use enough. I worked in a plant where we had a leaking Victaulic coupling on a 3-inch line carrying a propylene glycol mix freeze protected to at least zero degrees F. They built a cardboard box around the pipe and loaded it with dry ice nuggets. The only problem was the spot on the floor where they first put the dry ice, it lifted the epoxy coating on the concrete.

Dry is is SOLID CO2, so it is even colder than the liquid. As long as you can keep it in contact with the pipe, once freezing has occurred, it will hold the water until the solder joint is accomplished. But you might want to install a "tapped tee", (and plug), to allow for air expansion to be relieved, AND a point to drain the water if the joint is not successful after the ice blockage is thawed.