Water-filled Conduit

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Shoe

Senior Member
Location
USA
We have a schedule 40 type PVC service-entrance conduit that's filled with water and leaking into the building. A proposed solution is to seal both ends of the conduit to keep the water from infiltrating the building but leave the leaking conduit alone.

Is this typical? Is underground PVC conduit intended to be a water-tight installation or not?

Thanks.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Thanks. So I gather from this discussion that having water-immersed conductors in PVC pipes underground is typical and not something to be concerned about?

That would be my thought.
I rarely find a dry underground PVC conduit that had any age.
 
I rarely find a dry underground PVC conduit that had any age.

You found a dry one?? :D

The only dry-ish ones I find have a decent slope and one end drains into a mech. room or similar. (A 100' x 6" holds a lot of water, which is a real pain when you have to pull a large mic snake through it... had to empty the wet vac a couple of times on that one.)
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Depending on slope you may not be able to keep the water out by sealing the ends. The straight couplings on electrical PVC will leak. We deal with this by making a small hole in the PVC at grade on the backside. Sure the water drains at the foundation, but it gets wet anyway when it rains. We have sealed the PVC at the upper end of ther slope only and that has worked.
 

kwired

Electron manager
Location
NE Nebraska
A few things need consideration here.

1. is water coming from high level ground water? If so you probably have more water problems than just this underground raceway.

2. drainage around the building or structure. If water does not drain away from building very well it could follow raceway into structure either inside or outside of raceway.

3. is water entering at the outdoor end of the raceway? This could be for multiple reasons. Open ended raceway, no weatherhead, or cap on the weatherhead. Improperly oriented weatherhead. No drip loop in conductors that exit weatherhead. there could be other reasons

4. make sure you not only have drip loop in exposed conductors where they connect to service drop or other similar situations, but that the connectors used are arranged so they do not let water inside the conductor insulation, it will find a way through the conductor and into the structure eventually. Keeping the connections below the weatherhead effectively makes a plumbers "P" trap in the conductor and if the inlet is lower than the highest point of the trap the water will not flow past the trap. Pointing conductor ends downward so they will not let water inside conductor insulation is a good idea even if the connector is below the weatherhead.

5. condensation. This is pretty unavoidable, but if duct seal is used to prevent air migration through the raceway it should be much less of a problem than if there is no seal.
 

haskindm

Senior Member
Location
Maryland
You just discovered why underground conduit is "considered a wet location" and conductors must be "suitable for a wet location".
 
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