Mechanical (fluid) pipes from Mekanism can be used to push fluids into the machines, but the fluids can't be pulled out. This would be a feature request, but since they can be used to push fluids in, I'll assume it's a bug.

I couldn't find any documentation on this but eventually figured it out.

craft a "red rotation adjuster", use the sneak key to change its settings to "green liquid adjuster" or which ever color the machine uses, and right click the side you want to output from.