Getting waste uphill: your options
If the basement floor sits below the sewer line, the toilet can't drain by gravity. Minnesota's plumbing code (the 2018 Uniform Plumbing Code with Minnesota amendments, Minn. R. 4714.0050) allows these:
| Gravity drain | Sewage ejector pit | Macerating ("upflush") toilet | |
|---|---|---|---|
| When it works | Your main drain is low enough to slope to | Fixtures below the sewer | Allowed only in one- and two-family homes when gravity flow isn't possible |
| What it takes | Cutting the slab to run drain lines | A sealed pit with a bolted, gasketed cover, its own vent of at least 1½ inches, and a check valve and full-open shutoff valve on the discharge | A listed unit serving no more than one toilet, one sink and one shower or tub; watertight and gastight, kept accessible |
Sources: Minn. R. 4714.0710. Under the base code, an ejector taking toilet waste in a house must pump at least 20 gallons per minute and pass a 1½-inch solid, with at least a 2-inch discharge line (IAPMO, 2018 UPC 710.3).
Who can do the work
Minnesota requires plumbing to be done by a licensed plumber, except that a homeowner may do plumbing on the home they own and live in, unless a local ordinance forbids it (Minn. Stat. 326B.46). Either way it needs a plumbing permit: St. Paul says licensed plumbing contractors "must obtain permits to do any plumbing work," and homeowner permits must be applied for in person (St. Paul DSI). New electrical work needs a permit and inspection too (MN DLI).
Code basics for the room
- Ceiling height. In an existing basement, Minnesota requires 6'4" at the clear space in front of the toilet and sink, and over a 30-by-30-inch area where the showerhead is (Minn. R. 1309.0305).
- Exhaust fan. With no window, a bathroom needs an exhaust fan vented directly outdoors (MN Residential Code R303.3): 50 cfm if it's switched, or 20 cfm if it runs continuously (MN Mechanical Code Table 403.3.1.1). It can't dump into an attic or crawl space and needs a backdraft damper (MN Mechanical Code 501.3).
- Electrical. Minnesota adopted the 2026 National Electrical Code for permits filed on or after Aug. 17, 2026 (MN DLI). Bathrooms need a 20-amp circuit for the receptacles, GFCI protection, tamper-resistant receptacles, and no receptacle within 3 feet horizontally and 8 feet vertically of the tub rim or shower threshold (MN DLI 2026 NEC checklist).
Moisture
UMN Extension lists bathrooms as a source of basement moisture, says to ventilate them, and recommends keeping indoor humidity between 25% in winter and 50% in summer (UMN Extension, UMN Extension). A properly sized fan that's actually vented outside does most of that work.
Check your sewer backup coverage
The Minnesota Department of Commerce says neither flood insurance nor a typical homeowner's policy covers sewer backups; you need a separate endorsement (MN Commerce). The Insurance Information Institute says that coverage is available from most insurers for a nominal cost, and recommends a backwater valve installed by a qualified plumber (Insurance Information Institute). A finished basement with a bathroom has more to lose.
What it costs
Angi puts a basement bathroom addition at $10,000 to $15,000 nationally (Angi); its Minneapolis range for adding any bathroom runs much wider, from $5,240 to $78,600 with an average of $36,680 (Angi Minneapolis). For pieces of the job, Homewyse's St. Paul calculator (ZIP 55101, September 2026) puts a toilet drain line at $1,001–$1,217, not counting concrete work, and a bath fan with ducting at $391–$1,020 (Homewyse toilet drain, Homewyse bath fan). Whether you need an ejector, how far the fixtures are from the main drain, and how much slab has to be cut drive the cost most.
Is it worth it?
In NAR's 2025 report, adding a new bathroom recovers about 56% of cost and a basement conversion to living area 71% (NAR 2025). The Twin Cities basement remodel benchmark in the 2025 Cost vs. Value report, which includes a full bath, recouped 78.5% (Cost vs. Value). See finishing a basement.