Sterling Plymouth Plus Two-Piece Round-Front 1.6 GPF Toilet
Sterling Plymouth Plus Two-Piece Round-Front 1.6 GPF Toilet Review
The Sterling Plymouth Plus positioning — the legacy spec that still ships
The Sterling Plymouth Plus (402015-0) is a 1.6 GPF round-front two-piece toilet — and unlike the rest of the current Sterling lineup, it's NOT WaterSense certified. The Plymouth Plus is one of the few remaining Kohler-family toilets still produced at the pre-2014 federal flush spec of 1.6 GPF. At $110-$160, it's also the lowest-priced toilet in the entire Sterling residential catalog.
The Plymouth Plus exists for one specific buying scenario: replacing an existing 1.6 GPF toilet in a building with old, undersized, or under-graded drainlines where 1.28 GPF toilets have caused waste-carry problems. This is the toilet your plumber recommends when a 1.28 GPF replacement keeps clogging the drainline 30 feet downstream because the slope was set for 1.6 GPF flush volume.
Why 1.6 GPF still matters in 2026
The 1992 federal mandate dropped US residential toilets from 3.5+ GPF down to 1.6 GPF. The WaterSense voluntary spec (1.28 GPF) launched in 2007. State mandates for 1.28 GPF took effect in CA (2014), CO (2016), GA (2012), TX (2014), and NY (2014).
But pre-1992 building drainlines were sloped and sized for 5+ GPF. When those drainlines were re-piped to copper or PVC in the 1980s-1990s, they were sized for 3.5 GPF flush volume to maintain wastewater carry to the main stack. When the 1992 mandate dropped flush volume to 1.6 GPF, some long-run residential drainlines started exhibiting waste-accumulation issues — particularly horizontal runs over 25 feet at 1/8" per foot slope.
When WaterSense 1.28 GPF replacements get installed in these old-drainline buildings, the waste-carry problems can worsen. Plumbers in 1950s-1970s housing stock often recommend staying at 1.6 GPF replacement for this exact reason. The Plymouth Plus is the Kohler-family answer to "I need a 1.6 GPF replacement, not a 1.28."
What the Plymouth Plus delivers
- 3-inch flush valve with universal flapper compatibility (Korky 2032BP fits)
- 1.6 GPF — pre-WaterSense legacy spec for drainline-compatibility replacements
- MaP 1000g — top-tier bulk-waste performance (vs Windham's 700g)
- Standard 15" height — original toilet height before Comfort Height became standard
- Round-front bowl (16.5" front-to-back) — saves 2" of bathroom depth vs elongated
- 12-inch rough-in — US standard, universal compatibility
- Lifetime porcelain warranty — same terms as current Sterling lineup
- Manufactured at Kohler Wisconsin/NY plants — same Kohler quality oversight
Where Plymouth Plus is the right answer
- Pre-1980 housing stock with original cast-iron or galvanized drainlines still in use
- Long horizontal drainline runs (25+ feet) at minimum 1/8" per foot slope
- Replacement of an existing 1.6 GPF toilet in a building where 1.28 GPF retrofits have already caused problems elsewhere
- Rental properties where 1.28 GPF has caused tenant clog complaints
- States without 1.28 GPF mandates for replacements (most of the US outside CA, CO, GA, TX, NY)
- 1.6 GPF retrofits where the existing toilet was 3.5+ GPF — drainline carry was already adequate; no need to push below 1.6
Where Plymouth Plus is the WRONG answer
- New construction in CA, CO, GA, TX, NY — 1.28 GPF mandate disqualifies Plymouth Plus
- Owners seeking utility rebates — WaterSense certification required for $50-$200 rebates in CA, AZ, TX, NV
- Owner-occupied homes with modern drainlines — newer ABS/PVC drainlines designed post-1995 handle 1.28 GPF without issue
- ADA-compliant installations — Plymouth Plus 15" height fails accessibility code (17-19" required)
- LEED-certified or green-building projects — 1.6 GPF disqualifies LEED water-efficiency credits
Plymouth Plus vs Stinson — the key Sterling decision
| Spec | Plymouth Plus 402015-0 | Stinson 402080-0 |
|---|---|---|
| GPF | 1.6 (legacy) | 1.28 (WaterSense) |
| MaP | 1000g | 700g |
| Height | Standard 15" | Comfort 16.5" |
| Bowl | Round-Front | Round-Front or Elongated |
| WaterSense rebate | NO | YES ($50-$200 in many utilities) |
| ADA compliant | NO | YES (with Comfort Height variant) |
| Best for | Old-drainline replacements | New installs, modern drainlines |
| Price (~) | $110-$140 | $130-$180 |
The Plymouth Plus variant matrix
| Model # | Description | Price (~) |
|---|---|---|
| 402015-0 | Plymouth Plus, round-front, 1.6 GPF, standard 15" height, White | $110-$140 |
| 402015-96 | Same in Biscuit | $130-$160 |
| 402315-0 | Plymouth Plus elongated variant, 1.6 GPF, standard height | $130-$160 |
What's in the box
- Tank with pre-installed 3-inch flush valve + Fluidmaster-pattern fill valve
- Round-front bowl (16.5"), pre-drilled for 12" rough-in
- Tank-to-bowl gasket and brass bolts
- Chrome trip lever
- Wax ring NOT included
- SoftClose seat NOT included — Bemis 1500RD round-front universal ($30)
- Installation manual + Kohler/Sterling warranty registration
Install requirements
- Rough-in: 12 inches (standard).
- Weight: ~60 lbs total. Single-person install very comfortable.
- Standard two-piece install — Plymouth Plus does NOT require any special considerations vs Stinson or Windham.
- Universal aftermarket parts — Korky 2032BP (3-inch flapper) and Fluidmaster 400A fill valve fit directly.
- If replacing a 3.5 GPF toilet, check the drainline slope first — a 1.6 GPF flush in an old drainline with inadequate slope may not carry waste. If the existing toilet was already 1.6 GPF and worked fine, Plymouth Plus is a like-for-like swap.
What plumbers report
- Plymouth Plus is the "drainline-rescue" Sterling. Plumbers specifically request this SKU for old-housing-stock replacements where prior 1.28 GPF retrofits caused clog complaints.
- MaP 1000g — top-tier waste evacuation. Heavy paper loads, large solids — Plymouth Plus handles it.
- Standard 15" height is dated for adult households — most modern installs prefer 16.5"+ Comfort Height. The Plymouth Plus is shorter intentionally to match pre-1990s replacement profiles.
- Service life: 18-25 years porcelain. Same Sterling/Kohler quality, no compromise on porcelain.
- Parts service is identical to Stinson — universal Korky/Fluidmaster fit.
Where Plymouth Plus competes
| Competitor | Comparison |
|---|---|
| AmStd Mainstream 1.6 GPF Round ($150-$190) | Mainstream has AmStd brand recognition + 1.6 GPF option in same retail aisles. Plymouth Plus wins on price ($40-$50 less) and Kohler-family pedigree. |
| Kohler Wellworth 1.6 GPF Round ($180-$240) | Wellworth has direct Kohler branding + Class Five flush. Plymouth Plus wins on price ($50-$80 less) — same Kohler-family quality. |
| Mansfield Pro-Fit 1 Round ($150-$220) | Mansfield has commercial-grade quality + heavy 3.5 GPF heritage. Plymouth Plus has Kohler-family brand + lower price. |
| Glacier Bay 1.6 GPF Round ($89-$130) | Glacier Bay is the absolute lowest-price 1.6 GPF option but with 7-10 year service life. Plymouth Plus has 18-25 year service life + Kohler brand. |
The verdict
Buy Plymouth Plus if:
- Replacing an existing 1.6 GPF toilet in pre-1980 housing where drainline carry is a known issue
- State allows 1.6 GPF replacements (most US outside the 5 mandate states for new construction)
- You want the cheapest Kohler-family residential toilet on the market
- Round-front + standard 15" height fits the application (older households, half-bath retrofit)
- Rental property where tenant clog complaints with prior 1.28 GPF installs justify reverting to 1.6 GPF
Skip and choose Stinson if:
- Modern drainlines (1995+) — 1.28 GPF will carry waste fine
- You want utility rebate eligibility ($50-$200 in CA, AZ, TX, NV)
- Comfort Height (16.5") is important
- New construction in WaterSense-mandate states
Skip and choose Windham if:
- You want WaterSense 1.28 GPF + Comfort Height at similar low Sterling pricing
Warranty
Sterling Plymouth Plus residential warranty: 1 year on tank trim, lifetime on porcelain. Kohler-administered warranty service. Note: Plymouth Plus is not eligible for utility rebate paperwork that requires WaterSense certification.
Pricing reality (2026)
Plymouth Plus 402015-0 (White): $110-$140. Home Depot: $119-$149. Lowes: $109-$139. Build.com: $99-$129. Biscuit variant +$20-$30. Elongated variant (402315-0) +$20-$30. Property-management bulk: $79-$99 through Kohler Direct commercial channel.
- Legacy 1.6 GPF spec — for replacements where 1.28 GPF caused drainline issues
- Round-front bowl + standard 15" height
- MaP 1000g — top-tier bulk-waste performance
- Kohler-Sterling brand pedigree at sub-$160
- Universal aftermarket parts (Korky/Fluidmaster 3-inch fit)
- Lifetime porcelain warranty
- Stocked at every Home Depot and Lowes — easy replacement
- Lowest-priced Kohler-family 1.6 GPF residential SKU
- NOT WaterSense — 1.6 GPF disqualifies from utility rebates
- NOT ADA-compliant (15" standard height — too low for accessibility code)
- Round-front less comfortable than elongated for adult use
- Standard ceramic glaze (no Pure-Clean upgrade)
- Traditional flapper (not AquaPiston canister)
- SoftClose seat NOT included
- Banned for new construction in CA, CO, GA, TX, NY (1.28 GPF mandate)