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How do you keep a plastic expansion coupler waterproof ?

aligarjon

Hi guys

As the description

I need to run some black plastic conduit along the back of a house to feed some outside lights. The straight run is probably 10 to 12 meters with 3 or 4 fixed T boxes for drops to light fittings. I want to glue all the joints to keep any water out but was thinking of fitting some expansion couplers to stop it all twisting in the sun. Not something I have used before. How do you keep them water tight ? Or do they have some sort of rubber insert like plumbing fittings. Or does anyone have a better idea .

Thanks

Gary

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    unless it is perfectly sealed, it is often easier to leave it loose and to let the water out with a hole at a low point, perhaps with a swizzle of rock-wool or similar to discourage small insects.

    The other approach is install the clipping near right angles in a shape that allows the tube to distort to a slight  Z or S as it expands or contracts, or to have a section in flexi as bellows.

    However, these sort of things

    https://cpc.farnell.com/pro-power/ec20-black/expansion-coupler-20mm-x-125mm-black/dp/cbbr5153

    work perfectly well if the un-glued end is facing down, or horizontal but under something acting as a 'hat' to keep rain off.

    you could fill it with vaseline.....

    Mike.

    PS

    For steel the coefficient is 12E-6 per degree so for your 10m length changing in temperature from say 0 deg C to 40 deg C that 10m would expand by just over 4 mm if allowed to. For PVC the coefficient is more like  7E-5 so the same 10m length would expand by 2.4 cm, say  6 times as much.

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  • 0

    unless it is perfectly sealed, it is often easier to leave it loose and to let the water out with a hole at a low point, perhaps with a swizzle of rock-wool or similar to discourage small insects.

    The other approach is install the clipping near right angles in a shape that allows the tube to distort to a slight  Z or S as it expands or contracts, or to have a section in flexi as bellows.

    However, these sort of things

    https://cpc.farnell.com/pro-power/ec20-black/expansion-coupler-20mm-x-125mm-black/dp/cbbr5153

    work perfectly well if the un-glued end is facing down, or horizontal but under something acting as a 'hat' to keep rain off.

    you could fill it with vaseline.....

    Mike.

    PS

    For steel the coefficient is 12E-6 per degree so for your 10m length changing in temperature from say 0 deg C to 40 deg C that 10m would expand by just over 4 mm if allowed to. For PVC the coefficient is more like  7E-5 so the same 10m length would expand by 2.4 cm, say  6 times as much.

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