bite valve falling off?

How old is the Winter Kit? Maybe the valve is just stretched out a little? Contact Camelbak for a new valve? If it is defective, can they replace it? Or if you bought from REI, send it back.

I'd try those before I put any chemical adhesive near my mouth.

Are you sure you've got the Camelbak tubing mated to a Camlebak bit valve. They are usually a very tight fit.

After that, try plumbers teflon tape for a removable solution.

After that, perhaps food grade silicone applied to the tubing, not the valve, for a permanent solution.

the kit is new this winter, and the valve is a camelback brand valve. a friend suggested roughing up the tube just a bit with sandpaper – but not so much as to narrow the diameter. I do have the valve on the non-winter tube I could try on there too.

I just looked at a photo of the Camelbak Thermal Control kit, on the Camelbak website. It looks as if the "male" end of the bite valve is to be forced into the tube. You might try cutting off a half inch or so of the tubing and reinstalling the valve. Then use a very small zip tie as a hose clamp. Just my two cents worth.

I've had trouble with the bite valve on my MSR Dromolite bladder leaking at the valve/hose interface. The "insert" length was as short as in the Camelbak photo. I resorted to installing a Camelbak bite valve and the problem went away.

Is there a Camelbak bite valve, with a longer "insert", that you might retrofit?