Water and Ductbanks

[lile001]

We are running some underground conduit in ductbank between some buildings. One building is much higher than the other. I am worried that water, if it gets into the conduit by any means, will run down and get into the electrical gear at the downhill end. How could water get in, you say? well, let me count the ways:

Condensation build up over time
Unplanned flood at the uphill building due to repairs by 3-stooges Mechanical co. inc.
GroundWater infiltration into underground conduit due to poorly made joints

Is it common to put in water control features in concrete ductbank, such as a weep-hole at the lowest point in a concrete ductbank run, or would a weep hole in conduit just allow more water in, or worse violate the NEC?

--Lawrence

 

[brian john]

Larry;

It is not how water gets in, it is WATER GETS IN, heck water goes where and when it wants to.

OZ makes a conduit fitting that can withstand hydraluic pressure. The fittiing MUST be the proper one for conduit and cable type.

 

[Jim H]

Sometimes it is possible to insert a manhole or handhole just outside of the 'lower' building, and pitch the conduit 'downhill' into the manhole/handhole from both directions so it is the lowest part of the system.

Then, a drain hole in the bottom of the manhole, pea gravel fill under the manhole and most of the water problem is solved.

Of course, it's still a good idea to seal the entry unless the top of the manhole is below the conduit entry point.

 

[jinglis]

I agree with the manhole scenario being the best preventive measure. We have all had water migrate into a building through a conduit. I have one where the conduit enters directly above the main 600 volt switch. I would also look at the routing of the cables/conduits indoors. What if water does come in. I wouldn't want it running into the main switch. Perhaps an extra pull point beside/below the main switch with drip loops so the water can run off before it hits the switchgear.

 

[iwire]

The more detailed specifications I have read will have requirements about the pitch of underground conduits and requirements to have drain points in the low spots.

My way of looking at it is water will get in, deal with it's removal now and save yourself a lot of trouble later.

A manhole right outside with a lot of crushed stone under it just outside the low building seems prudent.