mini keg rubber bungs

I have had a 5L mini keg setup for a year or two now and it seems that the rubber bungs are starting to leak more and more.
They leak around the outside and not where the plastic insert is located.
What ends up happning is that it leaks and you run through the co2 cartridges before you can dispense out the beer quick enough.

Im not alking about me storing either, they leak now faster than I can pump out 1/2 the keg after tapping it.

I assume they have shrunk or something or time but does anyone know if this is a common problem?
Does anyone know a way to conteract the leaking?
Or any suggestions to help the seal?

I dont mind buying more but I hate to have to pay more the shipping than the cost of 5 bungs. Buying them also does fix the problem.

Thanks for any suggestions.

This may or may not be the answer you're looking for, but a book I have on building your own homebrew equipment suggested using a larger rubber stopper (the size of the hole) and a series of fender washers and a bolt/wing-nut combination -- SS of course!. They welded the fender washer onto the bolt at the head, inserted it through the stopper's hole, and put a second fender washer/wing nut at the top.

The welded washer/nut combo would grip before it spins, and by tightening the nut, the stopper would expand inside the hole to hold the pressure.

I would think that instead of welding, you might be able to epoxy them together, or at least use some food-grade silicone to make them stick enough to grip before they slipped...

Did that make sense? There are commercial plumbing products you can buy (for stopping up open drain pipes temporarily, etc) that you could look at for ideas. I wouldn't use them next to my beer though...

Hope that helps.

k.

I will look into it.
Now that I think of it, there must be a slow leak around it also, the beer hasnt been as carbonated as I would like either.