I am constantly having to replace my gunea pigs' bottles - they always start to leak. I think they must damage the end to make the ball bearing not fit perfectly. I have tried a couple of makes but still happens. Has anyone found a gunea pig proof bottle they could recommend?

what brands are you using?
i've personally never had any issues with the Classic Bunny bottles, so if you've not had those ones, could be worth a try?

(other than dropping them when full & breaking off the spouts - the night 6 of them broke at once was fun )

also how are they attatched to the hutch/cage?

I have the ones that are held on with a metal/plastic twisty thiny. Bought from more than one pet shop. Its not as if its one particular guinea pig - I have 3 hutches and it happens with all of them.
The amount we go through, I would happily pay more for better bottles, but the pet shops don't seem to have much choice.

are they these ones?

linky

i've found them to be very good, and most of mine yank on them like hell, so...
i have them mostly held internally by drain pipe clips(11 of them), but on the commercial hutches and extras on my hutches (a further 4) the wire hooks are used, they've never leaked
i had to buy rotastak brand out of desperation once, those leaked everywhere from new.

Yes, they are the ones. Maybe my guinea pigs are just extra rough, lol.

a bit strange really

you could just give them a bowl, or maybe if you just put a spare feed bowl under where the bottles hang, would keep your substrate dry, catching the leaks and the water clean as they're not putting their feet on the edges of the bowl to drink?