Guest bathrooms, floor drains, and laundry sinks have traps that hold water to block sewer gas. If one dries out, gas comes up. Pour a couple cups of water down each one.
Rock the toilet gently. If it moves or you see stains on the floor around the base, the wax seal underneath has failed and is letting gas escape.
Note when it's worst and where. A smell that spikes after heavy rain or sits in one bathroom tells a plumber a lot about the source.
Sewer gas isn't just gross, it can be flammable in high amounts. Air the place out. Pouring chemicals down the drain won't fix a vent or seal problem.
That rotten-egg smell means sewer gas is getting into your home somewhere it shouldn't. Every drain has a U-shaped trap that keeps a little water sitting in it as a barrier. In a spare bathroom or a floor drain that never gets used, that water evaporates, especially during a dry San Antonio summer, and the barrier disappears. Running water is often the whole fix.
When the smell won't quit, a plumber checks the things you can't see. Wax rings under toilets crack and dry out, common in older Monte Vista and Terrell Hills homes where the fixtures have been in place a long time. Vent pipes on the roof can clog with leaves or a bird's nest, which stops drains from breathing and pushes gas back inside. And a partial clog or a cracked line in the sewer main will make the whole house smell before it ever backs up.
Older neighborhoods sit on shifting clay soil that cracks cast iron and clay sewer pipe over time. If we suspect the main, we run a camera down the line to see exactly what's going on, whether it's a break, roots, or a belly in the pipe holding waste. That takes the guessing out of it.
Call sooner rather than later if the smell comes with slow drains, gurgling toilets, or backups. Those together point to the sewer main, and that's the kind of problem that gets worse and messier the longer it waits. We handle these across Schertz, Cibolo, Converse, and the rest of the San Antonio area.
Describe what you're seeing to a real San Antonio plumber: call (210) 555-0134 or send the form. Free, no obligation.