?Blow off for entire Lagering?

I'm preparing to do my first lager. I converted an old fridge, got the temperature controller, etc... My issue si that the 5 gal carboy takes up most of the head room in the fridge and i don't have room for a air lock. a folded over blow-off house works fine but I would have to use it for the entire two months. I'm not thinking it should be a problem if I switch the water every now and then. Any thoughts? Thanks

Using a blow-off would not be problem. I don't even think you need to switch the water, though I would anyway. For some additional protection, add some sanitizer to that water. Keep in mind that a blow-off tube is really just a big airlock.

Makes sense. Was thinking the same thing

The only thing I'd caution you about is when you reduce the temperature for lagering, and the beer cools, the stuff in the blow off jug will "suck back" into the beer.

You don't need an airlock for lagering, though, so you can just cover it with sanitized foil and a rubber band to hold it. That way you don't suck the water back into the beer. You can replace the blow off tube later, once the beer is cold, if you want to, but it's not necessary.

If you're going to do this a lot, you can construct a "remote airlock" by putting putting a double-drilled stopper in a small jar. The blow-off tube connects to one hole, and the airlock to the other. The jug can be empty if you like, but the tube should not be submurged. If anything sucks back through the airlock, it'll just drop into the jar instead of finding its way up the tube.

I've never tried it myself, but it's a clever idea. (I'd probably just go with foil during the cooling, though.)