how to waterproof metal conduit joints?

[saucyjack]

Hi guys; I've got to run 3x6mm singles through some exterior metal conduit (not actually installed yet, but will be approx. 7 metres in length with about 3 elbows), and wondered if anyone has any advice on making any of the joints (elbows, couplers etc.) weather/watertight? Any advice would be much appreciated!

 

[Adam W]

You could use cold galv spray on the threads to stop them going rusty, and rubber gasket seals under the box lids to keep the elements out. No point going nuts though - chances are you'll get a bit of condensation in there anyway, so if anything maybe worth putting a small drainage hole at the lowest point.

 

[malcolmsanford]

Hi guys; I've got to run 3x6mm singles through some exterior metal conduit (not actually installed yet, but will be approx. 7 metres in length with about 3 elbows), and wondered if anyone has any advice on making any of the joints (elbows, couplers etc.) weather/watertight? Any advice would be much appreciated!

To be honest have yet to see a properly installed conduit run leak. If you tighten the elbows up onto the threads then you won't get leaks. The same will go for the couplings.

As Novus said you could paint the threads after but if it's galv conduit you shouldn't get much rust. The same with the box gaskets if it's a normal outside enviroment then even not using the gaskets won't cause that much of a problem.

 

[saucyjack]

Thanks for the response guys, much appreciated and I'll keep the above points in mind.

 

[grantr37]

Hello, well if I was doing an outside conduit, the first thing I would do is all of my bending, sizing and forming, get the galvanised saddles fixed to the wall using stainless steel or Brass screws, then I would galvi paint all of the bends, as the original galvi crumbles off when you bend the tube, it fractures and flakes off, after that, I would get all my joining pieces together along with any bushes and lock rings.....
when you thread your tubing, use WD 40 instead of tallow, it cleans the threads as well as lubricating them, give them a scoosh every time you unwind the tap&die threading tool and give it a gentle tap as well, this will remove all the metal shavings, and the WD40 helps make manipulation and tightening easier, once you have your conduit ready, you should look up something on ebay called Liquid Levers, its quite expensive for the little sachets you get but its amazing stuff and always good to have in the toolbox, its American made stuff for waterproofing Electrical seals, a company up here in Scotland sells it on Ebay, you put a small amount of this on the thread before assembling the end boxes/through boxes onto the conduit etc and it forms an airtight waterproof seal, after you have assembled the through boxes and end boxes, if you have drilled through the back of any of them to fasten them securely onto the wall, put a little Galvi paint over the screw head inside the backbox/end box.....once you have got all of the tubing together and all tightened up, and wired it with your 3 singles, fit round rubber gaskets on with the Galvi metal lids, they only cost pennies and if you dont then the edges will eventually corrode inwards on the lids as they have a different electron displacement corrosion index than the tubing, due to being lighter and thinner metal (sacrificial displacement) and will end up acting like the sacrificial Anode on a boat Engine, if they corrode inwards, water starts seeping in from the edges.....this is only a problem in direct rain and rubber gaskets are not needed in areas under shelter with only air moisture content to deal with...
Once you have finished the tubing,give it all a quick coat of Galvi paint just to make sure that it lasts for a long time, and you can paint over this after about 2 hours with either Hammerite exterior paint (comes in tins as small as 250ml I think) or any colour of exterior gloss that suits the wall where its going, this will leave it looking the bees knees and well impress your customers...


Remember to take the round file to the ends of the conduit before you screw the end boxes on to get rid of any jagged bits on the inside edge, that will save you from stripping the insulation off the singles, if there are awkward turns in it and you dont want to pull too hard when wiring, I find that a bit of Fairy liquid does the trick and does not do any damage to the wires, dont use tallow for this as I have seen it done several times, it makes a mess everywhere and might even perish insulation after a short time...

 

[saucyjack]

Hello, well if I was doing an outside conduit, the first thing I would do is all of my bending, sizing and forming, get the galvanised saddles fixed to the wall using stainless steel or Brass screws, then I would galvi paint all of the bends, as the original galvi crumbles off when you bend the tube, it fractures and flakes off, after that, I would get all my joining pieces together along with any bushes and lock rings.....
when you thread your tubing, use WD 40 instead of tallow, it cleans the threads as well as lubricating them, give them a scoosh every time you unwind the tap&die threading tool and give it a gentle tap as well, this will remove all the metal shavings, and the WD40 helps make manipulation and tightening easier, once you have your conduit ready, you should look up something on ebay called Liquid Levers, its quite expensive for the little sachets you get but its amazing stuff and always good to have in the toolbox, its American made stuff for waterproofing Electrical seals, a company up here in Scotland sells it on Ebay, you put a small amount of this on the thread before assembling the end boxes/through boxes onto the conduit etc and it forms an airtight waterproof seal, after you have assembled the through boxes and end boxes, if you have drilled through the back of any of them to fasten them securely onto the wall, put a little Galvi paint over the screw head inside the backbox/end box.....once you have got all of the tubing together and all tightened up, and wired it with your 3 singles, fit round rubber gaskets on with the Galvi metal lids, they only cost pennies and if you dont then the edges will eventually corrode inwards on the lids as they have a different electron displacement corrosion index than the tubing, due to being lighter and thinner metal (sacrificial displacement) and will end up acting like the sacrificial Anode on a boat Engine, if they corrode inwards, water starts seeping in from the edges.....this is only a problem in direct rain and rubber gaskets are not needed in areas under shelter with only air moisture content to deal with...
Once you have finished the tubing,give it all a quick coat of Galvi paint just to make sure that it lasts for a long time, and you can paint over this after about 2 hours with either Hammerite exterior paint (comes in tins as small as 250ml I think) or any colour of exterior gloss that suits the wall where its going, this will leave it looking the bees knees and well impress your customers...


Remember to take the round file to the ends of the conduit before you screw the end boxes on to get rid of any jagged bits on the inside edge, that will save you from stripping the insulation off the singles, if there are awkward turns in it and you dont want to pull too hard when wiring, I find that a bit of Fairy liquid does the trick and does not do any damage to the wires, dont use tallow for this as I have seen it done several times, it makes a mess everywhere and might even perish insulation after a short time...

Phew! Thanks for all that info, I'll put as many of your points into practice as I can, 'cos apart from anything else I don't want to be running any of the cables/conduit etc. more than once!

 

[i=p/u]

the whole for moisture has to be at least 3mm

 

[mechelec]

if the installed environment will be so wet that you need to seal the conduit can you not just use plastic instead of galv.

 

[grantr37]

I think with it being mains and not telecom/Data or Selv, it would be dangerous to use plastic, also if its within reach of the public, you would probably get told to rip it down and re do it because the health and safety would say so....

 

[saucyjack]

It's only in 'normal' outside enviroment, so with the above advice I'm guessing it's all covered but I appreciate the comment. Was just thinking of worst-case scenarios really.

 

[mechelec]

I think with it being mains and not telecom/Data or Selv, it would be dangerous to use plastic,
Really well i have installed loads of "mains" in plastic im sure some others on here have to!!
also if its within reach of the public, you would probably get told to rip it down and re do it because the health and safety would say so....

I agree that depending on the position and pulic access then Galv may be required but the OP does not mention this

 

[mechelec]

I think with it being mains and not telecom/Data or Selv, it would be dangerous to use plastic,
Really well i have installed loads of "mains" in plastic im sure some others on here have to!!
also if its within reach of the public, you would probably get told to rip it down and re do it because the health and safety would say so
I agree that depending on the position and public access then Galv may be required but the OP does not mention this
....

.......................

 

[High Tower]

You could try pipe fitters compound that gas fitters use, if it will keep gas in, it should keep water out

 

[High Tower]

Pvc is fine for mains and fine for external use, only thing worth mentioning would be that if i was using it outside and its withing reach of the muppet public, i would use Heavy gauge type and solvent weld the joints. also decrease spacing and increase number of saddles used.

 

[Engineer54]

Well, ....i just don't know what to say after reading this little lot!!! Galvanised conduit has been around since the year dot, it's been installed just about everywhere it has been suitable for. So why in hells name do you think a galvanised conduit system needs special considerations because it's going to be installed externally... When it has been designed for just that purpose!!!!

Designed and erected/installed correctly the only additional protection required are the use of purpose made gaskets for the besa boxes etc. It has always been a requirement to coat any exposed conduit threads with a Zinc rich coating along with any box fixing screws. ....End of story!!!

What you should be more conserned about is condensation, which is far more likely to have detrimental affects. A 3mm or 4mm hole drilled at the installations lowest point(s) should alleviate that situation.


As a footnote on this thread, i haven't allowed the use of tight 90 degree solid or inspection elbows on any of my sites for well over 20 years. I'm pretty sure there not allowed via project specifications on any decent specified project in the UK either. Those fittings rip cable insulation to shreds when pulling cables round them. Much better using angle boxes or the slow 90 degree bends in a good conduit installation.
This also applies to Tee fitting also, much better again to make use of a Tee box.