The yeast in the Belgian Wit and Wheat Tripel can cause an aggressive fermentation which can lead to a blow-off, where the foam fills the whole bucket, and even finds its way out through the airlock. Don't panic, your brew is safe. As long as fermentation is in progress, CO2 creates a protective layer - like a blanket - over your beer. However, replace your airlock with a clean one as soon as possible. Or clean your current airlock and fill it with clean water.
To avoid this in the future, we recommend making a blow-off tube, using the following products:
010.002.4 – Three-piece airlock
018.055.0913.2 – Silicone hose 9 x 13 mm
004.402.x – Chemipro San
When you open the three-piece airlock, you can slide the silicone hose onto the protruding tube. Hang the hose in a bucket of water (with some Star San), and this way you create a large airlock, which can catch any blow-off krausen.