Given a leak with no valve upstream, what do you do without shutting off supply or draining any downstream vessel (like hot water cylinder)

What if there was a magnetic sand in the flow, that when a strong magnetic field is place through the pipe, that congeals to block the water in two places and allows access to a section. Any fix up needed, there after, is a breeze.The sand, of course, would be inert and washes out quickly.

There's only one severe problem.
-- wjt, Nov 10 2016

If a pipe has a leak, then what if you surrounded the leak with your magnetic sand/dust, and put the super-strong electromagnet on the other side of the pipe? Then the dust might enter the pipe through the leak/hole, and from there accumulate inside the pipe to block the water flow, enough that the leak could be repaired.
-- Vernon, Nov 10 2016


Could instead be an interesting way to unstop a clogged drain. Throw some iron-filing stuff down the drain (with the blessing of your local water and sewer utility) and with a rare-earth magnet on the outside direct it to the clog and scrub.

Or you could always just use a snake.
-- RayfordSteele, Nov 10 2016


The usual method is liquid nitrogen and a thermal blanket. There are many pipe freezing kits available specifically for plumbers in this situation.
-- mitxela, Nov 10 2016


They freeze the pipe solid? I thought that burst pipes.
-- bungston, Nov 10 2016


Well you're only freezing a few inches of pipe, so there's not much expansion really.
-- mitxela, Nov 10 2016


A hot pipe wouldn't freeze for very long but a nice solution.

[Vernon] I was thinking more along the lines of installing a valve for future proofing. The leak was in a regulator fitting.
-- wjt, Nov 10 2016


//The usual method is liquid nitrogen and a thermal blanket.//

You can also do it with dry ice, packed into a towel around the pipe. Lasts longer than freeze-sprays. However, if the leak is substantial, the flow of water will prevent freezage.
-- MaxwellBuchanan, Nov 12 2016


Frog spawn will seal a hole in a pipe as long as the water is cold, and you can wait around for long enough for a tadpole to form and block the hole. A longer wait for a frog to develop is required for a larger hole. This method won't work with boiling water.
-- xenzag, Nov 12 2016



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