Question about blow off tubes

[vrquick]

This morning I found my hefeweizen starting to bubble out of the airlock so I removed it and put a blow off tube in my bucket lid into a pot of bleach water. My question is how often do guys change the water that the blow off tube goes to. This is a very active fermentaion and the water is getting a little nasty already. Thanks for the help. Oh also how long should I use the blow off tube? I assume just until it settles down and then put the airlock back in.

 

[boo boo]

I leave it until the fermentation drops to the point of me removing the blow off and installing an airlock.