We had this issue only in part of our house that was serviced by a different hot water heater than the rest of our house. It can happen if your hot water heater wasn’t run for a while or if it needs a new rod. Search hot water heater smells like rotten eggs and you’ll find ways to clean it.

have you flushed your hot water heater and when was the last time you changed the rod?

Op here. It may be a hot water thing.

Dry trap, blocked rooftop vent, bacteria in drain lines, degraded anode in hot water heater.

DC tap is disgusting. Most people that I know that live in DC proper have entire house filtration systems and drink bottled water.

I think I know lol Do you notice a difference between smells in hot vs cold? Do this and report back results.

Go to a non smelly bathroom and run the cold water for 30 seconds. Do you smell anything? Test from a glass as well as just wafting the air. Now do the same with piping hot water, let it run for a minute or so and fill up a glass. Smell anything?

Do the same thing in the smelly bath. Notice any difference between bathrooms hot and cold? I’m very curious what you find.

We are in a DC rowhouse for about a year. While I’ve noticed the water seems quite hard (compared to the nearby apt where we lived for years), but odder is that I’ve noticed a smell on the second floor bathrooms. In one, I thought maybe it was stagnant water in both shower and sink. Vinegar seems to help. In the other bathroom, though, it’s almost like a sulfur-y, rotten egg smell when water first comes out. The first floor does not have these issues. I plan on looking into tests but I wonder if anyone has any thoughts. (By the way, we are in a central part of DC and this has been happening for some time so it’s not related to the recent water issues from the overflow.)