Important for Behind-the-Ear hearing aids:

Answer
Always separate the earpiece from the hearing aid before cleaning it. The hearing aid should never come into contact with water! When you connect the earpiece to your hearing aid, it has to be absolutely dry.

It is best to dry the tube with a puff of air using an air puffer (do not blow air through the tube from your mouth). You can get this inexpensive accessory from your local bonavox hearing specialists store.