said by whizkid3:For sealing the interior of the conduit, do so only if absolutely necessary.
Networks have a tendency to multiple like rabbits. Assume over time you will be adding more drops or using the conduits as wire chases for other things.
If you decide to seal the opening using something that is easy to remove so down the road it will be easy to open them up to pull more wires. With that in mind don't forget to leave a pull string.
/tom