I have double bathroom sinks - separate p-traps going into the wall for each
sink - each time I turn on the water in sink #2, there's a distinct rotten
egg smell, very briefly, that goes away once the water has been running for
a second or two - looking down into the trap from above the sink, before I
turn the water on, I can see standing water, so there's no sewer gas coming
in that way, right? What else should I check? Thanks!