Layout terms used here

Bi-level (split-entry)
Front door opens to a landing with half a flight up to the main floor and half a flight down to a partly below-grade lower level.
Tri-level
Three staggered levels, often with a lower family room and laundry a few steps below the main level, and sometimes a fourth basement level below that.
Garden-level
A lower level with windows partly above ground, common in bi-levels.
Lowest fixture
The drain opening closest to the sewer outlet elevation, usually a floor drain, laundry standpipe or lower bathroom.

Why these layouts take more damage

In a traditional ranch with an unfinished basement, a floor drain backup lands on bare concrete next to the furnace. In a bi-level, the lower level is usually finished: carpeted family room, one or two bedrooms, a bathroom and the laundry, often all within a few feet of the floor drain. Sewage reaching that floor spreads under carpet and into bedroom closets quickly.

Many of these homes in Thornton, Northglenn and Westminster were built in the 1960s and 1970s, and their lower levels have been remodeled more than once. Layers of flooring, paneling over drywall, and built-in shelving all add to what must be removed when Category 3 water gets underneath. A lower bathroom added during a remodel may also sit lower than the original drain and become the new overflow point.

Points to check in your own home

Lowest opening
Pour a little water in each lower drain and note which sits lowest; that is where a backup will show first
Laundry
A washer pumping into a standpipe next to the floor drain can push a partial blockage over the edge
Bedrooms
Anyone sleeping on the lower level should know the signs and what to do
Cleanout
Often in the utility room or outside near the foundation; know where before you need it

How it typically plays out

Illustrative example. Not a real job or customer.

In an illustrative bi-level, a teenager's lower-level bedroom shares a wall with the laundry room. During a long Saturday laundry run, the floor drain begins overflowing behind the closed laundry door.

  1. Water spreads under the laundry room door and wicks into the bedroom carpet pad before anyone notices.
  2. The household stops the washer, stops all water use and calls a plumber, who clears a blockage in the lateral.
  3. Cleanup removes carpet and pad in both rooms, the lower two feet of drywall on the shared wall, and a closet's contents.

Because nobody slept downstairs that night and the family stopped water use immediately, the damage stayed to two rooms rather than the whole lower level.

Lower-level habits that limit damage

  • Keep the laundry room door open when running the washer so overflow is noticed
  • Use hard flooring in the laundry and utility area rather than carpet
  • Leave a gap between storage and the floor drain
  • Ask a plumber whether a backwater valve fits the building drain
  • Consider a water alarm on the floor near the drain

General information for Thornton, not a quote or professional advice. In an emergency, call 911.