One-Piece Toilets
Updated February 20, 2026
Tank and bowl are fused into a single unit. Sleeker appearance with no seam between tank and bowl, making cleaning simpler.
Overview
One-piece toilets have the tank and bowl molded as a single unit. No seam between tank and bowl means no tank-to-bowl gasket to fail, no bolts to tighten, and a sleeker appearance. Easier to clean (no crevice where the tank meets the bowl), but heavier to handle during installation (60-100+ lbs vs 40-60 lbs for two-piece). Generally more expensive than two-piece toilets with the same features. The premium is for aesthetics and easier cleaning, not performance -- flush mechanisms are the same.
Pros & Cons
- Easy to clean
- Sleek design
- No tank-to-bowl leaks
- Heavier to install
- Higher cost
- Harder to ship
Key Features
- Tank and bowl molded as one seamless unit
- No tank-to-bowl gasket or bolts -- eliminates a common leak point
- Lower profile and sleeker appearance than two-piece
- Easier to clean -- no seam or crevice between tank and bowl
- Heavier than two-piece (60-100+ lbs) -- installation requires more effort
Sizing & Selection
Same rough-in and bowl dimensions as two-piece. 12-inch rough-in standard. Round or elongated bowl. Standard or comfort height. One-piece toilets tend to sit slightly lower in profile because the tank is integrated rather than stacked.
Installation
Same as two-piece except: no tank-to-bowl assembly step. The entire unit sets onto the flange at once. Heavier -- have a helper. The fill valve and flush mechanism install inside the one-piece tank cavity the same way as two-piece. Connect water supply and test.
Maintenance
- Same internal maintenance as two-piece: flapper, fill valve, flush valve.
- The advantage: no tank-to-bowl gasket to replace and no tank bolts to tighten.
- Clean the exterior with a non-abrasive cleaner. The seamless design makes wiping down faster.
- If the bowl or tank cracks, the entire unit must be replaced (unlike two-piece where you can replace just the tank or bowl).
Buying Tips
- TOTO Ultramax II is the benchmark one-piece toilet. Excellent flush, WaterSense certified, comfort height. -500.
- Kohler San Souci and American Standard Boulevard are also top-rated.
- Expect to pay -200 more than an equivalent two-piece model. The premium is for aesthetics and cleaning convenience.
- Weight matters for installation. If you are installing alone, a two-piece may be more practical.
- Skirted (concealed trapway) one-piece models look the cleanest but cost more and are harder to service at the base.