A friend is giving me an old 20L hiking ruck sack which he doesn't want.
I was originally in the market for a hydration ruck sack like the camelbak mule.
Just want to know if a normal rucksack would be good enough and just buy a hydration bladder.
Would the bladder stay stable in the ruck sack whilst out riding or would you recommend a special bag which has a compartment to fit the bladder ?
If you can get a bag for free that fits you there is no reason that you couild not make it work with a bladder.
If you are remotely handy with a needle and thread it should be easy enough to stich an old bit of boot lace into the back of bag near the top to hang a bladder from to stop it moving about too much. The other thing you would need to do is cut a hole in the top of the bag for the tube to come out. Looking at other bags i have the slit seems to be about 2-3cm wide and have an overlap of elastic to stop water getting in. Something like 1/2" wide elastic would be perfect for this and you would need less than 10cm which you may be able to blag as a sample from somewhere.
If you are really worried about the bladder moving you could put a couple of loos of elastic in the back to hold it against the back of the bag.
Camelback Unbottle?