How to patch this PVC elbow connection?
You can try a fiberglass "pipe repair kit" available at most hardware stores. You soak the fiberglass in water which activates the resin, and then wrap it around the leaking pipes. It will completely encase the pipes and harden, leaving you with a pretty strong temporary fix. I've used this on PVC and copper with good results; I think it would work on rubber tubing but you might want to check the label.

Note that it probably won't be practical to remove the fiberglass later and fix what's underneath, so only try this if you're planning to completely replace that section of pipes/tubing.

Example: http://www.homedepot.com/h_d1/N-5yc1v/R-100206252/h_d2/ProductDisplay?langId=-1&amp;storeId=10051&amp;catalogId=10053