Ah that’s unfortunate. I’ve never had issues with the red tubing, but seems like there might be batch variations between the tubing that might be causing slight leaking on the caps. Changing out the tubing would work.
I recommend smaller silicone tubing and probably a smaller barb (see Kishony’s morbidostat paper):
- Silicone tubing (1 mm inner diameter (i.d.), VWR, cat. no. 60985-708)
- Female Luer connector (Value Plastics, cat. no. FTLL004-6005)
I know its a hassle having to buy more parts. In the meantime, you might be able to borrow some syringe needles from the Khalil Lab. I’m sure they have some parts to spare, just to get started on some test experiments. I would remember to use silicone septas with the needles, since it helps holding the needles in place. You might need to add an extra needle to vent the vial (or not screw the vial as tight).
https://www.evolver.bio/t/recommendations-for-septas-and-needles/59