I have a whole extra piece that goes on top of that which has a much more solid place to put in a syringe and a little spigot-thing (I know there has to be another word for this but I don't know it) below that you turn to block the tube or open it. I got it from the hospital last time I was there and they even gave me an extra if I needed it. If you have this, you won't need ot open and shut the plastic cap you just keep it open (and the other piece is permanently screwed in).

You should NOT need a whole new tube inserted just because of this. You should be able to et this extra thingie somewhere.

This extra piece makes the whole tube a little bulkier BUT way less accidents and leakage since I've had it.