Deposits, despite good care

We loved these bottles ... used every day, washed out every day, leave now and then run into the dishwasher. Meanwhile, a mucous layer in the bottle that you just can not get away. We have tried to soak, dishwasher and everything, but you just can not get it away and the expensive bottle is simply unsuitable for drinking. After about a quarter of a pity. Then again returnable. The can be replaced safely and conveniently.