We sometimes have this problem in a shower we rarely use. The water in the trap dries out and then we get "that smell". To keep the water from evaporating, we dribble a little bit of vegetable oil down the drain after the water. The oil forms a little slick on top of the water and it does not evaporate. Keeps the smell and roaches away. Love this thread by the way. Especially descriptive Drewbert Write a book Drewbert...I'll sell it!