Frozen pipe under the cement slab what can I do?

Question

Only the kitchen sink line is froze. I have a no flow situation. Can physics help?

I don't understand why only the kitchen sink line (neighbors also). It's been extremely cold in the midwest.

Will a fish tank heater in the iron 5 inch pipe have enough watts to melt it? It's frozen in the 5 inch pipe that runs under the cement slab of the house.

Boiling water just makes the PVC pipes seals melt and leak.
Would sidewalk salt help? Is there a concern with the HCI (industrial drain stuff) that is still in the pipes and the sidewalk salt? Is there another chemical I can add?
Any information or ideas would be appreciated......

Answer 1

Dear Red,
If you can get at both ends of the iron pipe - try passing 4Amps (from an Isolating transformer or car battery) through it overnight. You only want gentle warming. A cast iron pipe may already be broken by the freezing ice - so look where your stopcock is in the street!
HCl and NaCl will corrode the Fe and you may not be able to stop it from holing your pipe in a few years time.

If the pipe is broken replace it in a slightly large polyethene tube so you can service it in future!

If you can't get at both ends all you can do is warm the concrete overblock - but this will take days. How long do your cold spells last?