Why do riad bathrooms sometimes smell?
The short answer
Dry water traps. That's it. Riads predate modern plumbing by centuries, and vent stacks that release sewer gas above the roof are nearly impossible to retrofit through metre-thick earth walls. Running water briefly through all the drains refills the traps and the smell vanishes.
You smell it at 3am. You've just arrived, the riad is beautiful, the courtyard has a fountain — and the bathroom smells like something died beneath the floor.
Nothing died. The floor drain dried out.
A water trap is a U-bend that holds a small reservoir of water between you and the sewer line. When the water evaporates, the trap becomes an open pipe. Sewer gas rises. In Marrakech, where summer air hits 45°C and guest bathrooms sit empty between bookings, a trap can dry out in days.
Running the tap for ten seconds. The smell stops. That's the entire fix.
But the trap is only half the problem. The other half is four hundred years old. Riads predate modern plumbing by centuries. The bathrooms you use were retrofitted into buildings designed for courtyard ablutions and hammam visits, not en-suite showers. A proper plumbing system needs vent stacks — vertical pipes that carry sewer gases above the roofline, where they dissipate harmlessly. Installing a vent stack means drilling vertically through walls built from pisé and stone, sometimes sixty centimeters thick. Most renovators don't. Most can't.
Without vents, gases that should exit through the roof escape through the nearest opening: the drain in your bathroom floor.
Then there's the network. Medina drainage connects multiple properties to shared channels that predate any individual renovation. A blockage three doors away pushes gases back through your drains. Your riad owner can maintain their plumbing perfectly and still inherit the smell from a neighbor who doesn't.