Our six year old basement bathroom, consisting of one sink, one toilet, and one shower has a continual sewer smell. It is especially strong in the summer and especially at the shower. This bathroom is not used much, mostly on the weekends. We have tried deodorizers which seem to help temporarily. Is there a permanent solution to getting rid of the sewer smell?

Most bad smells in tubs, lavatorys and showers are caused by rotting hair matted with grease from the soap. Try this for the smell. Tonight before bedtine Take a 1/2 gallon of bleach and pour it down the drain and let set over night. Next morning ,(and this is important) flush out the drain with two large pans of boiling water to loosen the grease and flush the mess out. The bleach will make the hair slippery and began to dissolve it and the hot water will melt the grease and flush the mess away.
Also, pull the lavatory stopper and look down the drain. About 4 inches down you'll see a small rod sticking out. Fish out any hair that's caught there and do the same thing to the lavatory if you detect any odor. This should make your drains smell better. Good luck, Tom