How do you thaw the underground supply water pipe.

[TheOldFellow]

Did all the right things. Left the (sealed system) heating on, turned the water stopcock off, drained down the cold water system right to the stop-c*ck.

After five days returned to no supply at the drain-down just 3 inches above the stop-c*ck which is just 4 inches above the slab.

United Utilities says they are very busy, and they might call me back in a few hours to take details. Sounds like a long wait.

So how can I move the thawing of the supply pipe forward? The

15mm black plastic incommer is gently curving as it enters the slab, so pushing a thaw-pipe in is going to be hard. Is there any electrical way - water does conduct a little?

I suspect, that like the electricity supply, it isn't buried far enough. So I might be into trenching.....

I hate winter.

R.

[The Natural Philosopher]

Yes, well..

I would say that what you need to do is apply gentle heat - fan heater - to pipe below stopcock.

Even if it is MDPE, it will still conduct a little.

Chances are that is where the ice is.

When you say stopcock, I assume opu mean your won internal one, not one in the street..

[Skipweasel]

Light a bonfire on top of it?

[cynic]

Change your service pipe to lead then connect a small welder output across the section from street stoptap to indoor stoptap just as we had to do in 1964 when the problem was common all over the country. This new fangled plastic pipe is no good for passing enough current to create heat :-)

[Fredxx]

On the other hand ice is more resistive than water, so any current you can pass into the stopcock will largely heat only the plugs of ice. Assuming the plug of water the other side is earthed somehow! It might also be a good idea to isolate the internal piping first.

Anther advantage of plastic pipes is that they are largely transparent to microwaves, though the idea of a magnetron with it's power supply outdoors is perhaps a little beyond DIY!!

[Mike Clarke]

No chance of getting an earth through water in a plastic pipe if it's more than a metre or so long.

[Fredxx]

What sort of "earth" are we talking about? What sort of current would pass at a few kV? In practice it would depend heavily on the purity of the water. My comment is that the resistivity of ice is even higher, such that all the voltage, and hence power, would be dropped across any plug of ice.

[Frank Erskine]

The water company could dose the supply with ethylene glycol.

Or common salt.

[Skipweasel]

What if it has an expansion joint?

[Frank Erskine]

3 dB loss

[TheOldFellow]

Yes, the internal one. The one in the street is 50 metres away. The pipe is black plastic, but there is only 3 inches showing above the slab.

I guess you are saying that the ice is likely to be nearest the house, as that is where it rises towards the surface. Trouble is that it had gentle heat on it the whole time I was away (the plinth heater, wet, is opposite.) Still I'll try that, if today's thaw doesn=E2=80=99t start a dribble.

R.

[newshound]

Going off at a tangent, the local pet-shop had anti-freeze for bird drinkers. Claimed to contain "no harmful glycol or glycerol". I suppose it could either have been brine or ethanol, neither of which sound that good for the little birdies...

[Skipweasel]

Propylene glycol. Like Ethylene glycol, but not harmful. Sadly, also more expensive.