Gel pumps and pipes
Gelpumps
Gelpumps are a part of the underground theme and they are used to transport gel to the surface.
Gelpumps are easy to make and they are very cool. You can find a prefab here: http://forums.steampowered.com/forums/showthread.php?t=1920931 The prefab has sounds pipes and a button.
gelpumps can be made out of these prop's:
place this where you want it:models/props_underground/pump_station.mdl (this is the pump)
place this prop on the side of the pump: models/props_underground/paint_distillery_tank.mdl (this is the tank on the side of the pump)
place a bended pipe on the otherside of the pump and a straight pipe on the top of the pump and you will get something like this: http://steamcommunity.com/id/commander_D/screenshot/540644195468243489/?tab=all.
heres a movie:http://www.youtube.com/watch?v=MWi5028qsK8
pipes are props and most of them is called paint_tube etc...
theres many diffrent pipes wit diffrent lod settings.
place them in your map and rotate them and move them so they are connected to whatever you want it to lead to.