Conduit for underground cable

[syl]

I'm wiring up an outbuilding to the house and have spoken with a sparkie who will do the clever bit (including hookup of SWA and testing). I'll do some digging. The sparkie wasn't bothered about it, but I want to put the cable in conduit, as it saved me having the drive dug up earlier in the year when the electric companies incoming concentric cable shorted itself out and burned through.

The longest run is approximately 40m underground (18" deep) and the cable is three core 10mm2 SWA.

What conduit is best, at a reasonable price? I was thinking 63mm twin wall.
I forgot to ask him - How should I "seal" the end of the conduit around the cable, in an attempt to stop it filling with water, prior to him coming back to connect it all? Or shouldn't I bother?

 

[RF Lighting]

63mm twin wall should be fine.

Remember to keep any bends to a minimum, and if you do need a bend such as where the cable comes out the ground, keep it a long gentle swept bend. Big SWAs don't go round corners!

The most important thing is to make sure you put a good strong draw rope in the duct before you lay it.

You could gaffer tape a rubble bag or similar over the ends of the duct if you like to keep it clean and dry inside.

 

[ban-all-sheds]

Put 2 ducts in - you might decide you want phone or network cables out there.

 

[syl]

I might even put three in (black for power, blue for water and green for some cat5). It's getting more expensive...

 

[ban-all-sheds]

I thought it was grey for telecomms - green is cable TV?

Better get some orange too, in case you want to light the path to the building.

 

[syl]

I can watch TV over cat5 these days. I couldn't find the grey stuff in 50m twinwall anyway - but if black is cheaper I might just use that. I could get away with 50mm, or even less, for the cat5 too.

Once it's all installed, should I stop up the ends around exiting cables/pipes - shove a bit of paper (or something else) down and then silicone sealant? The conduit will rise from the ground externally against a wall.

 

[ban-all-sheds]

Where it/they comes out of the ground, run it inside length(s) of drainpipe - looks a lot nicer, and take them up into an enclosure mounted on the wall.

 

[DetlefSchmitz]

I put in a couple of underground conduit runs a couple of years ago, garage to new shed. I brought both ends up inside the buildings (very gentle curves), which made the wiring job a lot easier. Might not be so easy doing that into a house though.