VERY strong sewer odor

For years we often noticed a bad smell when we stopped somewhere and we always suspected the toilet. Last year I learned that the P-traps in showers are often very small and can dry out in time or splash out in transit. Our solution is a tight-fitting rubber plug in the drain when the shower is not in use, and to send some water down the drain whenever we stop.

As for chemicals, we've never used them. We're fans of the Geo Method; it's always worked well for us and our 8-year-old tank sensors still work perfectly.