If you’re choosing between the TOTO Washlet KS6 and S5, you’re staring at two of TOTO’s most compelling mid-range seats right now.
Both share nearly identical technology under the hood — but the differences in design, footprint, and positioning are real enough to matter to you.
| Feature | TOTO Washlet KS6 (SW3946) | TOTO Washlet S5 (SW3446) |
|---|---|---|
| Image |  |
 |
| Dimensions (L x W x H) | 25-5/16″ x 15-1/4″ x 11-13/16″ | 24-3/8″ x 17-9/16″ x 7-7/16″ |
| Water Heating | Instantaneous (tankless) | Instantaneous (tankless) |
| PREMIST | Yes | Yes |
| EWATER+ Wand Cleaning | Yes (wand only) | Yes (wand only) |
| User Presets | 4 | 4 |
| Night Light | Yes | Yes |
| Colors Available | Cotton White only | Cotton White + Sedona Beige |
| Buy Now |  |
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1. TOTO Washlet KS6 (SW3946)
The KS6 is TOTO’s newest mid-range WASHLET and the direct replacement for the popular K300 — and it brings a distinctly design-forward identity to the lineup.
Where the K300 played it practical, the KS6 leans into sculpted aesthetics, a minimalist silhouette, and what TOTO calls “quiet luxury.”
It still delivers the same core TOTO hygiene package you’d expect — instantaneous tankless heating, PREMIST bowl misting, and EWATER+ wand cleaning — but it wraps it in a form that looks noticeably more refined on the toilet.
Features
- Instantaneous tankless water heating — continuous warm water from the first second
- PREMIST automatically mists the bowl before each use to reduce waste adhesion
- EWATER+ self-cleans the wand with electrolyzed water before and after every use
- CLEAN RESIN coating repels grime on the wand and seat surface
- Four user memory presets on the wireless remote
- Heated SoftClose seat with five temperature settings
- Warm air dryer with five temperature settings
- Automatic air deodorizer and soft night light
- Sculpted low-profile silhouette with seamless seat design
- WASHLET+ compatible for cord-concealing installations
Pros
- Visually distinctive — the most “designed” looking WASHLET at this price tier
- Full TOTO hygiene suite: PREMIST + EWATER+ + CLEAN RESIN
- Seamless seat eliminates hard-to-clean gaps
- Four presets make it ideal for multi-person households
- Illuminated remote can be handheld or wall-mounted
Cons
- Taller rear profile (nearly 12″) may be noticeable on lower-profile toilets
- Cotton White only — no Sedona Beige option
- Newer model, so fewer long-term user reviews than the S5
Check its current price on Amazon
2. TOTO Washlet S5 (SW3446)
The S5 is TOTO’s current mid-range flagship and the direct replacement for the widely-loved C5 — and it earned the 2025 Wirecutter top pick for electric bidet seats almost immediately after launch.
It improves on the C5 in every meaningful way: instantaneous tankless heating replaces the old tank system, the profile is 19% slimmer, and it adds a fourth user preset and a night light that the C5 never had.
If you’ve been eyeing the TOTO C5 vs S5 comparison, the verdict is clear — the S5 is the current generation and the smarter long-term buy.
Features
- Instantaneous tankless water heating — endless warm water on demand
- PREMIST coats the bowl before every use to prevent waste from sticking
- EWATER+ cleans the wand with electrolyzed water before and after each use
- CLEAN RESIN coating keeps the wand and seat surface hygienic with less effort
- Four user memory presets via wireless remote
- Heated SoftClose seat with five temperature settings
- Warm air dryer with five temperature settings
- Automatic air deodorizer and soft night light
- Seamless seat design with rounded corners — easier to keep clean
- WASHLET+ compatible — conceals power cord and water line with compatible toilets
- Available in Cotton White and Sedona Beige
Pros
- 2025 Wirecutter Top Pick — independently validated as the best electric bidet seat
- 19% slimmer profile than its predecessor — lowest-profile seat at this tier
- Available in two colors, giving you more flexibility to match your bathroom
- Seamless seat is noticeably easier to clean than older bidet designs
- Full hygiene suite on par with the KS6 at a more accessible price point
Cons
- Wireless remote wall cradle is slightly bulkier than some minimalist setups prefer
- No EWATER+ bowl cleaning (that feature is reserved for the S7 and above)
- One-year limited warranty is standard but shorter than some competing brands
Check its current price on Amazon
Design and Build Quality
This is where the KS6 and S5 diverge most visibly — and it comes down to philosophy.
The KS6 was designed to be a statement piece.
Its sculpted silhouette and carefully contoured form were built to “blend seamlessly into both classic and contemporary spaces,” as TOTO describes it — and in practice, the KS6 simply looks more architectural on a toilet than most bidet seats do.
The tradeoff is height.
At nearly 12 inches at the rear, the KS6 sits noticeably taller than the S5, which measures just 7-7/16″ at its highest point.
The S5 went the other direction entirely — its redesigned profile is 19% slimmer than the C5 it replaced, and it sits much closer to the toilet bowl for a cleaner, more integrated look.
If your toilet is lower-profile, or if you’re pairing your WASHLET with one of the TOTO wall-hung toilet options, the S5’s lower stance will look and feel more natural.
Both seats use TOTO’s seamless seat design, which eliminates the gap where dirt collects on older bidet designs — a genuine cleaning improvement worth noting.
You can read more about how TOTO’s design philosophy has evolved in our TOTO color and finish guide.
Winner: Tie — The KS6 wins on sculptural aesthetic presence; the S5 wins on low-profile integration.
Hygiene Technology
At the core hygiene level, these two seats are functionally identical.
Both deliver instantaneous tankless warm water — a major upgrade over the tank-type C5 that used to run cold after 30–60 seconds, as we detailed in the C5 vs S7 breakdown.
Both use PREMIST to pre-wet the bowl before every use, which dramatically reduces how much waste sticks to the ceramic.
Both use EWATER+ to sanitize the wand with electrolyzed water before and after every use.
And both apply CLEAN RESIN coating to the wand and seat surfaces to passively repel grime.
What neither seat does — and this is worth being clear about — is extend EWATER+ treatment to the bowl itself.
That bowl-level EWATER+ misting is exclusive to the S7 and S7A, which we compared in our S7 comparison guide.
If passive bowl cleaning between uses matters a great deal to you, you’re looking at the wrong tier.
For the mid-range buyer, though, both the KS6 and S5 deliver the best wand hygiene available at their price point — and PREMIST keeps the bowl meaningfully cleaner than nothing at all.
Winner: Tie — Identical hygiene tech across both seats.
Comfort and Controls
Both seats are equally equipped in the comfort department.
You get a heated SoftClose seat with five temperature levels, a warm air dryer with five temperature settings, an automatic air deodorizer, five spray settings (rear soft, rear cleanse, front cleanse, oscillating, pulsating), and a soft night light that makes late-night visits noticeably easier.
Both remotes support four user memory presets — a practical upgrade if more than one person uses the toilet regularly.
This is the same quad-preset system that the Brondell Swash 1400 comparison highlighted as a standout feature of the current S-series lineup.
The KS6’s illuminated remote can be held or wall-mounted.
The S5’s remote also wall-mounts in a slim cradle and has everyday controls on the front face with setup buttons hidden on the back — a subtle but thoughtful design.
For users with limited mobility or who simply prefer not to reach for the seat controls, either remote works excellently.
Our guide to the best heated bidet toilet seats covers what to look for in seat warmth if this is your top priority.
Winner: Tie — Identical comfort specs; both remotes are practical and wall-mountable.
Installation and Compatibility
Both seats are designed for standard DIY installation on most elongated North American toilets.
You attach the baseplate, connect the included T-connector to your toilet’s water supply line, and plug into a nearby GFCI outlet.
Most installations take under an hour, and no plumber is required.
Both are WASHLET+ compatible, which means they work with TOTO WASHLET+ ready toilets to conceal the power cord and water supply hose for a completely clean, cable-free look — a meaningful consideration if you’re doing a full bathroom refresh.
The key physical difference: the KS6 requires at least 2 inches between the tank and the seat mounting bolts — standard on most toilets, but worth measuring.
Neither seat supports auto-flush natively.
For that feature, you’d need to step up to the S7 with a compatible TOTO T40 WASHLET+ toilet, which we covered in our C5 vs S7 comparison.
If you’re still choosing between a bidet seat and a full integrated toilet, the bidet toilet seat comparison chart gives you a broad side-by-side view of the market.
Winner: Tie — Installation is identical; both WASHLET+ compatible.
Color Options
The S5 has a clear edge here.
It’s available in both Cotton White (#01) and Sedona Beige (#12), giving you more flexibility to match warm-toned bathroom décor.
The KS6, at this time, is only offered in Cotton White.
If your bathroom has beige or earth-toned fixtures, this matters more than you’d think.
Our TOTO color comparison guide walks through the difference between Cotton White and Colonial White (a warm shade found on older TOTO models), and explains what to look for when matching shades.
Winner: S5 — More color choice makes it the more flexible option for bathroom matching.
Verdict — Which One Should You Buy?
Both the KS6 and S5 are excellent bidet seats, and neither will disappoint.
But they serve subtly different buyers.
Buy the TOTO Washlet KS6 if…
You want the most visually distinctive WASHLET at this price tier.
You prioritize a sculpted, architectural look in your bathroom.
You’re replacing a K300 and want its direct, feature-matched successor.
You’re pairing it with a contemporary toilet where the KS6’s taller aesthetic presence will complement the overall design.
Check its current price on Amazon
Buy the TOTO Washlet S5 if…
You want the independently validated, Wirecutter-approved choice in this category.
You prefer a lower-profile seat that sits closer to the bowl for a cleaner, integrated look.
Your bathroom fixtures are available in Sedona Beige and you need that color option.
You want TOTO’s most popular mid-range model with the largest community of verified owners.
Check its current price on Amazon
Frequently Asked Questions
Is the KS6 actually replacing the K300?
Yes. The TOTO Washlet KS6 is the direct successor to the K300 and replaces it in TOTO’s current lineup.
It shares the same core hygiene features — PREMIST, EWATER+, instantaneous heating — while adding CLEAN RESIN, a seamless seat design, and a more sculpted aesthetic.
If you were considering the K300, the KS6 is the current and more refined version to buy.
You can also compare the S5 vs K300 breakdown to understand where the KS6 fits relative to both legacy models.
Is the S5 really that much slimmer than the KS6?
The difference is meaningful.
The S5 stands just 7-7/16″ at its highest rear point, while the KS6 reaches nearly 12 inches.
On a standard toilet, that height gap is visible.
The S5’s lower stance gives it a more integrated appearance — especially if you care about how your bidet seat looks from across the bathroom.
The KS6’s taller profile is part of its distinctive design identity, but it’s a real trade-off if low-profile is a priority for you.
Our guide to bidets for existing toilets covers fit and profile considerations in more detail.
Do both seats work with non-TOTO toilets?
Yes — both the KS6 and S5 install on most standard elongated North American toilets, regardless of brand.
You’ll need to confirm your toilet has a relatively flat tank-to-bowl junction (not a “French curve”) and at least 2 inches of clearance between the tank and the seat mounting bolts.
WASHLET+ cord-concealment features only activate when paired with TOTO WASHLET+ compatible toilets.
For a broader view of compatibility, our bidet toilet seat comparison chart walks through fit requirements across multiple models.
Which has the better hygiene features between the two?
They’re identical at the hygiene level.
Both use PREMIST, EWATER+ wand cleaning, and CLEAN RESIN — TOTO’s complete mid-tier hygiene stack.
Neither extends EWATER+ to bowl cleaning — that’s an S7-exclusive feature we broke down in the C5 vs S7 comparison.
If you’re choosing primarily on hygiene performance, either seat will deliver the same result.
The choice between KS6 and S5 ultimately comes down to design preference, profile height, and color availability.
Conclusion
The TOTO Washlet KS6 vs S5 is a rare comparison where both products sit at nearly the same technology level — and the decision hinges almost entirely on how you want your bathroom to look and feel.
The S5 is the safer, independently validated pick.
It’s slimmer, lighter in profile, available in two colors, and carries a Wirecutter top-pick badge that makes it the default recommendation for most buyers.
The KS6 is the more striking choice.
It’s the most design-conscious WASHLET at this price tier, and if you want a seat that reads as a premium bathroom fixture rather than an afterthought, the KS6 earns that distinction.
Either way, you’re stepping into TOTO’s current-generation hygiene stack — and that’s a significant upgrade from whatever you’re replacing.
Browse the full bidet comparisons archive for more head-to-head guides, or check the best bidets for home use roundup if you’re still exploring your options.
