Why does my drain smell like sewage?

A sewage smell from a drain usually means the P-trap has dried out or there is a sewer gas leak. P-traps hold water that blocks sewer gases from entering your home. If a drain is rarely used, pour water down it to refill the trap. If the smell persists, the trap may be damaged or the vent pipe may be blocked. Check for leaky or loose pipes under the sink. A blocked vent stack on the roof can also force sewer gases back into your home.