Floor drains are the unsung workhorses of residential plumbing — they sit in basements, utility rooms, garages, and laundry areas, ready to handle water from a water heater failure, washing machine overflow, or flooding event. Because they’re used infrequently and out of sight, they’re also among the most neglected fixtures in a home. The result is a predictable set of problems: dried-out traps that let sewer gas into living spaces, clogged strainers, and drains that fail to drain when they’re actually needed.

The P-Trap: The Most Important Thing to Maintain

Every floor drain has a P-trap — a curved section of pipe that holds a small amount of water to create a seal against sewer gas. In frequently-used drains, this trap stays full automatically. In floor drains that rarely see water, the trap water evaporates over time, breaking the seal and allowing hydrogen sulfide and other sewer gases to enter your home. If you’ve ever noticed a rotten-egg or sewage smell coming from a basement or garage floor drain, a dried-out trap is the most likely cause.

The fix is simple: pour a gallon of water down the drain every few months to refill the trap. Some homeowners add a small amount of cooking oil or a commercial trap primer solution to slow evaporation further. In Denver’s dry climate, trap evaporation happens faster than in more humid regions, so this refresh is worth putting on your maintenance calendar — every 60 to 90 days is a reasonable interval for infrequently used drains.

Strainer and Drain Cover Cleaning

Most floor drains have a metal strainer or grate covering the drain opening to catch debris. This strainer needs to be lifted out and cleaned periodically — debris accumulation restricts flow and, if organic material sits in the strainer, can contribute to odors. Remove the strainer, rinse it, scrub off any buildup, check the drain opening below for visible debris, and reinstall. This is a five-minute task that significantly reduces the likelihood of the drain backing up when you actually need it.

Periodic Drain Flushing

Even with a clean strainer, sediment and residue can accumulate in the drain pipe below the trap over time. Running a hose into the floor drain and flushing it with water once or twice a year helps clear this buildup and confirms that the drain is actually flowing freely. If water backs up or drains very slowly, there’s a blockage in the line that needs professional attention before it becomes a problem during a real flooding event.

  • Refill the P-trap with water every 60–90 days for infrequently used drains
  • Remove and clean the strainer cover every few months
  • Flush the drain with a hose once or twice a year to clear sediment
  • Check that the drain flows freely before storm season or any anticipated high-water risk
  • Address slow draining promptly — don’t wait for a backup during an actual emergency

When to Call a Plumber

If flushing the drain produces slow drainage or a backup, there’s a clog somewhere in the drain line that a plumber’s drain snake or hydro jetting equipment can clear. If the sewer gas smell persists after you’ve refilled the trap multiple times, the trap itself may be damaged or the drain may have a venting issue that requires professional diagnosis. And if your floor drain has a backflow check valve — which older Denver-area homes with lower-lying basements sometimes have — that valve needs to be tested periodically to ensure it will actually close and prevent sewer backup during a city main surcharge event.

Done’s plumbing and drain team serves the entire Denver metro area and can clear floor drain blockages, camera-inspect drain lines, and address persistent odor or backup problems. Learn more on our drain cleaning page. For stubborn blockages, hydrojetting is often the most effective solution. If you have concerns about sewer line condition beyond the floor drain, our sewer services team can help. Contact Done to schedule a drain service.