Kohler San Souci Compact One-Piece Elongated 1.28 GPF Toilet

The Kohler San Souci positioning

The San Souci (K-4007) is Kohler's compact one-piece elongated toilet — designed for bathrooms where a full-elongated one-piece (18.5") wouldn't fit but the buyer still wants the seamless one-piece aesthetic + AquaPiston canister flush. At $420-$580, the San Souci sits between the entry-tier value one-pieces (Highline Arc Curv at $420-$580) and the designer-tier one-pieces (Memoirs Stately at $720+).

The San Souci's compact-elongated bowl (17.5" front-to-back) makes it the right Kohler one-piece for apartment bathrooms, condo half-baths, and new-construction tract houses where floor depth is limited but the buyer wants more than a basic two-piece. It's the natural alternative to the Maxton K-31621 for buyers who prefer rounded classical-contemporary styling over Maxton's skirted-trapway modern aesthetic.

San Souci design language

• Rounded one-piece silhouette — softer curves through the tank-to-bowl transition than the angular Maxton
• Visible classical-contemporary detail — subtle architectural curves without committing to fully traditional (Memoirs) or fully modern (Maxton/Gleam)
• Compact bowl footprint — 17.5" front-to-back fits bathrooms with 26-27" floor depth
• Comfort Height (17.25") — adult-friendly seat height while keeping bowl footprint compact
• Top-mount or front-mount trip lever options depending on configuration

San Souci vs Maxton — picking between compact-elongated Kohler one-pieces

The choice between San Souci and Maxton is design-driven: San Souci for classical/transitional aesthetics, Maxton for modern. Engineering is essentially identical (same AquaPiston canister, same compact-elongated bowl size, same 1.28 GPF).

The San Souci variant matrix

The AquaPiston canister at this price tier

The San Souci uses Kohler's AquaPiston canister flush valve — same vertical cylinder mechanism that's in Memoirs Stately, Maxton, Adair, Cimarron Comfort Height (AquaPiston variant), Elliston, Gleam, Corbelle, and the smart-toilet lines (Veil Smart, Numi 2.0, Karing). Engineering details:

• 360-degree water release during flush for uniform bowl-cleansing
• Quieter flush than traditional flapper mechanisms (no flapper "slap")
• Service life: 12-15 years for the canister vs 5-7 years for traditional flapper
• Easier replacement when canister wears — pull-out from top, drop-in replacement, no tank removal (30-minute DIY)
• Kohler GP1138930 canister kit ($35-$65) for replacement
• NOT universal-aftermarket compatible — Korky/Fluidmaster canisters don't fit AquaPiston Kohlers; order through Kohler customer service or supply houses

What's in the box

• One-piece bowl + tank molded as single porcelain unit (~95 lbs)
• Pre-installed AquaPiston canister flush valve
• Chrome trip lever (front-mount or top-mount depending on configuration)
• Standard ceramic glaze on bowl interior
• Wax ring NOT included
• SoftClose seat NOT included — Kohler Brevia compact-elongated ($45-$70) or Cachet Quiet-Close compact ($90-$140) recommended
• Installation manual

Install requirements and procedure

• Rough-in: 12 inches (standard).
• Weight: ~95 lbs as single unit — two-person install recommended; single-person feasible with a furniture dolly.
• Visible trapway design (not skirted) — floor flange access is easier than skirted-trapway one-pieces. Mounting bolts visible from above with bolt caps.
• Wax ring: standard wax ring works fine; horn-style ($6) more forgiving of slightly-low flanges.
• Floor must be flat — out-of-level floor can crack porcelain. Use Korky setting compound ($6) if needed.

The install procedure (75 minutes, two people preferred)

1. Remove existing toilet. Scrape wax ring off floor flange. Inspect flange — verify at or just above finished-floor level.
2. Install new wax ring on flange.
3. Two people: lift San Souci straight down onto wax ring. Press straight down with no twisting.
4. Use new floor mounting bolts (included) to anchor bowl to flange. Hand-tight + 1/4 turn maximum — never overtighten on porcelain.
5. Reconnect supply line to bottom of tank.
6. Open shutoff valve. Tank fills (60-90 seconds via AquaPiston canister). Test flush several times.
7. Check for leaks at supply, around bowl base (wax ring seal), and at canister housing inside tank.
8. Install seat (sold separately).
9. Apply silicone caulk around base of bowl (optional but recommended).

What owners report

• The compact one-piece + classical styling is the buying logic. Owners specifically choose San Souci when full-elongated wouldn't fit but Maxton's modern look doesn't suit the bathroom design.
• AquaPiston canister flush is quiet and effective. MaP 800g for normal household use.
• The visible trapway makes floor flange access easier than skirted-trapway models — meaningful when wax ring eventually needs replacement.
• Standard ceramic glaze shows hard-water spots in mineral-heavy regions — same trade-off as other Class Five and AquaPiston Kohlers without Pure-Clean.
• Service is straightforward. AquaPiston canister replacement at 12-15 years (Kohler GP1138930, $35-$65, 30-minute DIY). Universal Fluidmaster 400A fill valve at 10-12 years.
• Tank lid replacement (if cracked) runs $140-$220 for current production.
• Service life: 25+ years porcelain.
• The compact bowl size works well for typical adults but feels noticeably smaller than full-elongated for users over 6 feet tall.

Where San Souci wins vs other Kohler one-pieces

• Compact one-piece in classical-contemporary aesthetic — unique niche within Kohler's lineup
• Easier floor flange access than skirted-trapway Maxton/Gleam/Corbelle
• Lower price than Memoirs Stately at similar AquaPiston + comfort-height spec

Where San Souci loses

• No included SoftClose seat — Maxton at lower price includes one
• Higher price than Highline Arc Curv K-3493 at similar one-piece + AquaPiston level (though K-3493 is full-elongated, not compact)
• Standard ceramic glaze — no Pure-Clean upgrade available
• Compact-elongated may feel small for taller adult households

Where San Souci competes

The verdict

Buy San Souci if:

• Bathroom is space-constrained (compact-elongated bowl matters)
• You want classical-contemporary one-piece aesthetic (not Maxton's modern skirted)
• AquaPiston canister flush is preferred over Class Five flapper
• Floor flange service access matters (visible trapway easier to work around)

Skip and choose Maxton if:

• You prefer modern skirted-trapway aesthetic + included soft-close seat
• Budget under $400 — Maxton is the same AquaPiston canister at $80-$100 less

Skip and choose Santa Rosa if:

• Same compact one-piece + AquaPiston spec at lower price floor with slightly different exterior styling

Warranty

Kohler San Souci residential warranty: 1 year on tank trim, lifetime on porcelain, 5-year on AquaPiston canister mechanism. Standard Kohler customer service.

Pricing reality (2026)

San Souci K-4007-0 (White): $420-$500. Home Depot: $449-$499. Lowes: $429-$479. Build.com: $399-$459. Biscuit/Almond +$40-$80. Black Black +$80-$140 (special-order).