Due to a move I had my bed completely empty and saw under the microscope out of curiosity the water a little bit. It was crystal clear and completely odorless, almost like fresh from the tap. I thought it was almost a shame to pour it away - you could use it problemos on. A look into the mattress offered no cause for criticism. The fleece was white as the day, also I could see his fingers no deposits / algae on the inside. Of course, this "inner" impressions are limited due to the small shutter opening, but I consider them to be representative of the rest of the bed.
Since I do not own a double waterbed, but a simple, stocks for proud four years is sufficient. Thanks to the included vinyl cleaner can also combine the cleaning of the inside with the same from the outside.