Any reason why not?

[Munch]

I am coming to the end of my gallon jar of homemade pickled onions

Is there anything stopping me re-using the vinegar and just chucking a load more onions in?

I have got the vinegar to perfection, with added chillis and wotnot and just think it would be a waste throwing it away.

This is of course if I can find pickling onions at any other time of year except xmas

[Hilary B]

As with a different pickling question, there may be less acid in your vinegar than there was for the previous batch (even more likely with onions than with eggs), and you need sufficient acid for it to work safely. Whether the reduction in acid content is sufficient to be a problem is a complex issue. I wouldn't risk it....

[Flummery]

I might try it once but not more. The vinegar does draw moisture from the things you're pickling so over time it becomes more dilute. Eventually it wouldn't be strong enough to preserve the onions and you could get them rotting.

I find it far superior to ordinary vinegar on chips though!

[Munch]

I find it far superior to ordinary vinegar on chips though!

What a great idea? sometime I wish I was clever! lol