A floor drain provides a low point in the floor where water can safely exit the space through the drain system rather than pooling, seeping into the slab, or flowing toward finished areas. In a basement or garage, floor drains protect against water intrusion from a variety of sources — a water heater or washing machine that fails, a backed-up utility sink, a burst pipe, snowmelt tracked in from vehicles, or a heavy rain event that finds its way into the space. They are a simple fixture, but an important one: when water enters unexpectedly, a working floor drain is often the difference between a minor cleanup and significant water damage.

Basement Floor Drains

Basement floor drains are particularly important in Colorado homes, where temperature swings can cause pipes to freeze and burst during a cold snap, and where spring snowmelt can raise groundwater tables enough to stress older foundations. A water heater, boiler, washing machine, or utility sink in the basement all represent potential water sources that can discharge significant volume if something goes wrong. The floor drain gives that water somewhere to go quickly. Many older Denver-area homes have a floor drain that connects directly to the main sewer line, which keeps water moving out of the space efficiently as long as the drain is maintained and the trap is not dry.

Garage Floor Drains

In a garage, the floor drain handles water that comes in with vehicles — rain, snow, and ice melt — as well as any incidental spills from maintenance activities. This is especially relevant in Colorado, where road-treated vehicles come in with significant moisture during winter months. Garage floor drains typically connect to a dry well or a municipal stormwater system rather than the sanitary sewer, because they are designed to handle water rather than sewage. This distinction matters: if a drain appears to connect to the sanitary sewer in a garage, there are environmental and code compliance considerations that a licensed plumber should evaluate.

The P-Trap: Why You Need to Keep It Wet

Like any fixture drain, a floor drain has a P-trap beneath it that holds a water seal to block sewer gases. Floor drains in infrequently used spaces — a basement that rarely sees water, a guest bathroom on a lower level, or a garage — are prone to having their trap dry out over time. When the water seal evaporates, sewer gases can migrate up through the drain into the space. If you notice a rotten-egg or sewage odor in a basement or garage, a dry floor drain trap is often the cause. The fix is simple: pour a quart or two of water down the drain every few months. Adding a small amount of cooking oil helps the seal last longer by slowing evaporation.

Common Floor Drain Problems

  • Dry trap allowing sewer gas into the space — solved by regularly pouring water down the drain
  • Slow or blocked drain from sediment, debris, or root intrusion in the line
  • Drain backing up during heavy use of other fixtures — often a sign of a partial main line blockage
  • Cracked or deteriorated drain body in older homes with clay or cast iron connections

When to Have Your Floor Drain Inspected or Serviced

If your floor drain backs up when you run the washing machine or flush a toilet, that is a strong signal of a partial blockage in the main sewer line — floor drains are often the first place a backup appears because they sit at the lowest point in the drain system. This warrants a sewer camera inspection to find the cause, followed by drain cleaning to clear it. If the drain simply runs slowly or you’ve never had it looked at in a home built before 1980, a camera inspection is a reasonable proactive step to confirm the line is clear and intact.

Done’s drain team handles floor drain service and main line inspections throughout the Denver metro. If your basement or garage drain is backing up, slow, or you’re catching a sewer smell, reach out through our drains and sewer services page to get it sorted out.