When to replace "blow off" hose with airlock?

Greetings!

I'm making my first batch and following, more or less, the instructions in "The Joy of Home Brewing." Last night I added my yeast before going to bed and attached the 1.25" hose to allow for blow off. This morning it had blown off a little bit of foam, etc. into the jar I put at the other end. Although there is lots of bubbling and activity still in the glass carboy it does not look like it is high enough to go out the plastic tubing any longer. So my question is, although it has been less than 24 hours, can I replace the hose with the airlock or should I give it the 2-3 days that the book says? Maybe it froths up more later or maybe it's too slow to see?

Thanks for any tips.

Welcome to the forum!

If the krausen has started to slow down, then it is OK to replace the blowoff with an airlock. However, just to be safe, I would leave the tube on for the next 2 to 3 days anyways. It's cheap insurance against mopping wort off your walls and ceiling. On my last batch I left the blowoff tube on for two weeks and it hadn't even reached the top of the carboy.