Uniseal bulkhead

[fishdance]

Dunk the uniseals in some warm water to expand the rubber just before you push the pipe through. Adding some olive oil and a sanding a slight bevel on the end of your pipe will also help you push through.
However since your only using gravilty feed drains, I would just dangle the pipes into the main stormwater pipe without any seals at all. You don't need the join to be waterproof. example If you size your drill hole carefully, it will be splashproof which is all you need.
Or add a little silicon glue on any that are drilled too large.

 

[kamikaziechameleon]

Actually got to test the Uniseal this weekend and it worked perfectly as a 1" to 4" adapter. We even tested it briefly under some real water pressure without any issue or leaks springing. My partner in crime was plowing this weekend and then our sump filter bag hanger broke so we had some obstacles. All the fittings are purchased, we have the cut lengths calculated, all we need is to fix the sump and then we buy, cut, and glue this thing together.