As above the black placky ones won't leak if they are good quality and in decent nick, same as fuel jerrys shouldn't! I've also used them for years in the mil and on trips and not had any probs.

The black army 20 ltr are the dogs.

You just need to get new caps and the leaks stop.

OK, I believe you, but the ones I had were brand new and all 4 of them leaked when turned on their side - quite drastically.

So I'll look for another solution - seems there are many different things available.