Colorado · typical $150–$450
Basement & floor drains
The basement floor drain is the lowest opening in most Colorado homes, which makes it the first place a sewer problem shows up. Water rising out of it is almost never about the floor drain itself; it's a sign that the main line beyond it is blocked.
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Sounds like this?
- Water coming up through the basement floor drain
- Water around the drain when the washing machine empties
- A sewer or rotten-egg smell from the drain
- The drain gurgles when upstairs toilets flush
- A laundry or utility sink that drains slowly
What the floor drain is telling you
| What you see | Most likely cause |
|---|---|
| Water rises when the washer drains | Partial clog in the main line or the laundry branch |
| Water rises when upstairs toilets flush | Main sewer line blockage |
| Sewer smell, no water | Dry trap: the water seal has evaporated |
| Water around the drain after heavy rain | Groundwater or a downspout connection, not a clog |
| Drain is slow on its own | Debris, lint or sediment in the drain body |
The dry trap smell
Colorado's dry air evaporates the water seal in a floor drain that's rarely used, especially in a furnace room. Once the trap is dry, sewer gas comes straight up into the basement. Pour a gallon of water into the drain, then a tablespoon of mineral oil to slow evaporation. If the smell comes back within days, the trap or a vent may need attention.
Laundry and utility sinks
Basement laundry lines collect lint, which acts like hair in a shower drain. A lint trap on the washer discharge hose costs a few dollars and prevents most of these clogs. If the laundry standpipe overflows while the washer pumps out, it's either undersized or partly clogged; a plumber can tell which.
Common questions
Why is water coming up from my basement floor drain?+
Usually because the main sewer line is blocked and water from the rest of the house has nowhere else to go. Stop using water and call.
Why does my basement floor drain smell like sewer?+
Most often the trap has dried out. Refill it with water and a little mineral oil. If it persists, have the trap and vent checked.
Is water from a floor drain dangerous?+
If it's from a sewer backup, yes; treat it as contaminated. Keep people and pets away and avoid electrical hazards.
Can I install a backwater valve?+
Yes, a plumber can install one so sewage from the city main can't flow back in. It typically requires a permit.