Dimensions / Building materials / Toilets / Two-piece toilet
A two-piece toilet is a separate tank bolted onto the bowl. Makers build it for a 12 in (305 mm) rough-in, the distance from the finished wall to the centre of the outlet (American Standard, TOTO), with 10 in and 14 in models for other drains. Elongated two-pieces run 27-3/4 to 30-9/16 in long and round-fronts 26-3/8 to 28-1/4 in, 1-3/8 to 2-1/2 in shorter within a family; they stand 28-1/4 to 33-1/2 in tall to the tank lid, with the rim at 14-1/2 to 15 in for standard height or 16-1/8 to 16-1/2 in for comfort height. The bowl and tank ship apart: TOTO’s Drake II bowl weighs 57.3 lb and its tank 31.5 lb.
| Rough-in | Length, elongated | Heaviest piece (TOTO Drake II) |
|---|---|---|
| 12in305 mm | 27-3/4–30-9/16in | 57.3lb |
Sources: Kohler, TOTO, American Standard. Checked October 2026.
A 12 in rough-in two-piece, the drain and room measured in the bathroom and a 4.8 L single flush are filled in; change the rough-in, what you measured, the code or the flush.
Rough-ins and carrier depths are the makers’ printed minimums; clearances are the model plumbing codes, which a local code may change.
A 12 in rough-in toilet needs at least 12 in (305 mm) from the finished wall to the centre of the flange (American Standard, TOTO); you measured 12-1/2 in (318 mm), so the tank sits 1/2 in further from the wall than drawn.
American Standard designs its two-pieces to a 12 in minimum from the finished wall to the outlet centre.
IPC 405.3.1 asks for at least 15 in (381 mm) from the toilet’s centreline to a side wall or obstruction and 21 in (533 mm) clear in front of it; you have 16 in and 24 in.
IPC 405.3.1: 15 in to a side wall and 21 in in front; the UPC asks 24 in.
WaterSense, and the laws of California, New York and Washington, allow an effective flush of 4.8 L (1.28 gpf). This toilet flushes 4.8 L.
Kohler’s Highline Arc K-78279 flushes 4.8 L (1.28 gpf), the WaterSense ceiling.
Selling two-piece toilets? Photograph the toilet assembled and the bowl and tank in their cartons, mark length, width, height, rough-in and carton sizes in SizeMarker, and send the picture with your offer.
Mark a photoLength is from the back of the tank to the front of the bowl, height to the tank lid, rim to the bowl rim without a seat. TOTO figures are read from its drawings.
| Model | Length | Width | Height | Rim |
|---|---|---|---|---|
| Kohler Highline Arc K-78279This page | 29-9/16 in (751 mm) | 18-1/16 in (459 mm) | 30-3/8 in (772 mm) | 16-1/2 in (419 mm) |
| Kohler Cimarron K-3609Elongated, 12 in | 29-1/2 in (749 mm) | 17-5/8 in (447 mm) | 30-3/4 in (781 mm) | 16-1/2 in |
| Kohler Cimarron K-3887Round-front, 12 in | 27-1/4 in (692 mm) | 17-5/8 in (448 mm) | 30-1/2 in (775 mm) | 16-1/2 in |
| Kohler Wellworth K-3998Elongated, 12 in | 30 in (762 mm) | 18 in (457 mm) | 29-1/4 in (743 mm) | 14-1/2 in (368 mm) |
| Kohler Wellworth Classic K-3577Round-front, 12 in | 27-1/2 in (699 mm) | 19-5/8 in (498 mm) | 28-1/4 in (718 mm) | 14-1/2 in (368 mm) |
| Kohler Highline Classic K-3493Elongated, 12 in, 1.6 gpf | 30-9/16 in (776 mm) | 21-1/4 in (540 mm) | 31-1/4 in (794 mm) | — |
| American Standard Champion 4 HETElongated, 12 in | 30-1/4 in (768 mm) | 17-7/8 in (454 mm) | 31-3/16 in (792 mm) | 16-1/2 in |
| American Standard Champion 4 731BRound-front, 12 in | 28-1/4 in (717 mm) | 17-7/8 in (454 mm) | 31-3/16 in (792 mm) | — |
| TOTO Drake IIElongated, 12 in | 28-1/2 in (724 mm) | 17-1/4 in (438 mm) | 30 in (761 mm) | 16-1/8 in (410 mm) |
| TOTO Drake CST744E / CST743EElongated / round, standard height | 27-3/4 / 26-3/8 in | — | 28-1/2 in | 14-5/8 in |
| TOTO CST424Elongated | 28-1/4 in | — | 33-1/2 in | 16-1/8 in |
| Sterling Windham 402368Elongated, 14 in rough-in | 31-11/16 in (805 mm) | 17 in (432 mm) | 28-1/2 in (724 mm) | 15 in (381 mm) |
Sources: Kohler · Kohler · Kohler · Kohler · Kohler · Sterling · Kohler · American Standard · American Standard · TOTO · TOTO
No US code sets a rough-in: it is the maker’s figure, measured from the finished wall.
| Item | Figure |
|---|---|
| Rough-inAmerican Standard; TOTO | At least 12 in (305 mm) from the finished wall to the centre of the outlet or closet flange |
| 10 in modelsKohler; TOTO | Kohler Cimarron K-3851, 27-1/4 in long; TOTO Drake MS776124CEFG.10 |
| 14 in modelsSterling; TOTO; Kohler | Sterling Windham 402368, 31-11/16 in long; TOTO models ending .14; Kohler Corbelle with 10 and 14 in rough-in kits |
| Gap drawn behind the tankKohler; TOTO | K-78279 13/16 in (21 mm), K-3577 1 in (25 mm), K-3851 1-1/4 in (32 mm); TOTO Drake II 3/4 in (20 mm) |
| Depth from the wallOur calculation | Length + the drawn gap + how far the drain is beyond the rough-in: K-78279 29-9/16 + 13/16 = 30-3/8 in |
| Measure fromTOTO | The finished wall, not the baseboard |
Sources: Kohler · TOTO · Kohler · TOTO · TOTO · Kohler · Kohler · Kohler · American Standard
| Item | Figure |
|---|---|
| Two catalogue partsKohler | Bowl and tank are separate items: the Cimarron K-3609 is the K-4309 bowl and the K-4421 tank |
| Two cartonsTOTO | Drake II bowl 57.3 lb and tank 31.5 lb in separate cartons, 88.8 lb in all (our sum); the one-piece UltraMax II ships as 99 lb in one |
| Tank-to-bowl jointTOTO installation manual | A gasket on the flush valve nut and two brass bolts, tightened until the tank touches the bowl at three points |
| TallerKohler; American Standard (our comparison) | Cimarron 30-3/4 in against 28-13/16 in for the one-piece; Champion 4 31-3/16 in against 29-1/2 in |
| Round or elongatedSame family (our comparison) | Elongated is 1-3/8 to 2-1/2 in longer: Cimarron 27-1/4 / 29-1/2 in, Wellworth 27-1/2 / 30 in, TOTO Drake II 26-1/2 / 28-1/2 in |
Sources: Kohler · American Standard · TOTO · TOTO · Kohler · American Standard
| Item | Figure |
|---|---|
| SideIPC 405.3.1; UPC 402.5 | 15 in (381 mm) from the centreline to a side wall or obstruction; 30 in (762 mm) centre to centre |
| FrontIPC; UPC as adopted in Washington | 21 in (533 mm) under the IPC; 24 in (610 mm) under the UPC, 21 in in dwelling units |
| CompartmentIPC | 30 × 60 in (762 × 1524 mm) for a floor-mounted toilet |
| Accessible seatADA 604.4; TOTO drawing | 17–19 in (430–485 mm) to the top of the seat; the Drake II seat is 17-1/2 in over a 16-1/8 in rim |
| US federal flush10 CFR 430.32 | 1.6 gpf (6.0 L) |
| WaterSense flushVersion 1.2 | 1.28 gpf (4.8 L) effective; a dual flush counts two reduced flushes and one full |
Sources: ICC · Washington State Legislature · US Department of Justice · American Standard · govinfo · EPA WaterSense
Elongated two-pieces from Kohler, TOTO and American Standard run 27-3/4 to 30-9/16 in long and round-fronts 26-3/8 to 28-1/4 in; they stand 28-1/4 to 33-1/2 in tall to the tank lid. Kohler’s Highline Arc is 29-9/16 × 18-1/16 × 30-3/8 in.
Most are built for 12 in (305 mm): American Standard designs to a minimum of 12 in from the finished wall to the outlet centre. Kohler makes the Cimarron in a 10 in version and Sterling the Windham for 14 in; TOTO marks such models .10 or .14.
In the same family, 1-3/8 in (TOTO Drake) to 2-1/2 in (Kohler Wellworth). The elongated bowl gives a longer seat in the extra length.
TOTO’s Drake II ships as a 57.3 lb bowl and a 31.5 lb tank in two cartons, 88.8 lb together. A one-piece ships whole: TOTO’s UltraMax II is 99 lb in one carton.
Makers draw it: 13/16 in on Kohler’s Highline Arc, 1 in on the Wellworth Classic, 1-1/4 in on the 10 in Cimarron and 3/4 in on TOTO’s Drake II. A drain set further out than the rough-in adds to it.
Both heights are made: Kohler’s Wellworth has a 14-1/2 in rim, the Cimarron and Highline Arc 16-1/2 in. ADA measures 17–19 in to the top of the seat; TOTO’s Drake II seat is 17-1/2 in over a 16-1/8 in rim.
A US buyer orders a two-piece by its rough-in, 12 in or a 10 or 14 in version, and expects the bowl shape and overall length, width and height, the rim height, the trapway, the flush volume and its WaterSense listing, the bowl and tank model numbers, and the size and weight of each carton. Mark those on a photo of your own toilet with SizeMarker, like the picture at the top, and share one card in WhatsApp or WeChat.
