I've recently noticed a stale water smell coming from one of the bathrooms in my 7-year-old house. I've checked the plumbing and there aren't any leaks that I can find. Interestingly, I've also detected the smell, though to a lesser extent, in our spare bathroom. The exhaust fans aren't the best, but I doubt they're to blame. I've even installed access panels to better check the plumbing. My wife thinks I'm a bit obsessed, but I'm certain about the smell!
3 Answers
Have you checked the condition of your water heater? Sometimes old units can cause funky smells, so it might be worth a look.
Try running the water in the sink, bathtub, and shower, plus flush the toilet. If those bathrooms aren’t used often, the p-trap water can start to smell. If you use them regularly, check around the walls and ceiling for any signs of dampness.
It could be a mildew smell you're dealing with, which can happen if there’s been a long-term leak somewhere, even if you can't see it. Keep an eye on that!
I don't think it's mildew—I can usually detect that pretty quickly!

What exactly should I be looking for on the walls and ceiling? My wife uses the bathroom daily, and above it is just the attic, with no visible water damage.