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Bidet to fit a Kohler toilet: check your model, then choose

Most Kohler two-piece toilets take a bidet attachment like any other toilet. The trouble is with some Kohler one-piece toilets, like the Rialto and San Raphael, whose bowl curves up into the tank with no flat ledge behind the seat. Find your model number inside the tank, check whether it's one-piece with a curved back, and you'll know in five minutes. Kohler also publishes its own fit grid for its bidet products.

Here's how to find your model, what each kind of Kohler toilet needs, and what to do when yours is the hard one.

Step 1: find your Kohler model number

Everything else is easier once you have the number.

Take the tank lid off and set it somewhere it can't fall. It's heavy and it breaks.
Look on the inside back wall of the tank. Kohler model numbers are usually molded into the china or stamped in blue or black ink. They're four or five digits, sometimes with a K in front (K-3810, for example).
One-piece toilet: that number is the toilet's model number.
Two-piece toilet: the number in the tank is only the tank's. The bowl has its own number, molded under the bowl's flange at the back. For a bidet, the tank number plus "two-piece" is usually enough.
Can't read it? Older tanks get mineral buildup; a scrub helps. Some tanks have a foam liner that hides the number; the tank lid's part number or the serial number can stand in, and Kohler's customer care can look it up from those.

Type the number into a search with "Kohler" in front. The product page tells you the family name (Cimarron, Highline, Santa Rosa, San Raphael…), whether it's one-piece or two-piece, round or elongated, and which seat it shipped with.

Step 2: sort it into one of four kinds

Your Kohler is…	How to tell	Bidet attachment?
Two-piece, flat deck	A separate tank bolted onto the bowl, a flat area behind the seat bolts	Usually yes. Measure the tank gap.
One-piece, flat deck	No seam between tank and bowl, but a flat ledge of about 1.5 in behind the bolts	Often yes. Check the flat strip and the water inlet room.
One-piece, French curve	The bowl sweeps up into a scooped tank front, no ledge. Often shipped with Kohler's "French Curve" seat.	Usually no. See bidet for a French curve toilet.
Skirted or wall-hung	Smooth sides hiding the trapway; or a bowl on the wall with no tank	Skirted: often yes on the seat side, check the water. Wall-hung: hard.

Kohler toilets bidet sellers call hard

Kohler's own product pages say which toilets ship with a French Curve seat. Those are the ones bidet sellers warn about.

Rialto (K-3386, one-piece, round front). Ships with a French Curve seat. One bidet seller says only two bidet seats on the market fit it, in the round size, and even those overhang the front by about 1.5 inches. Most attachments won't sit flat.
San Raphael (K-3384 elongated, K-3467 round, one-piece). Ships with a French Curve seat. Buyers disagree: one reports an all-metal attachment working on the elongated one-piece, another says that same kind of attachment doesn't fit Kohler one-piece French curve toilets at all. Treat it as "check before you buy".
Santa Rosa (one-piece, compact elongated). Kohler's own compatibility grid marks some of its bidet products yes and others no for it. A bidet seat seller lists a few third-party seats that fit it. Compact bowls leave little room behind the bolts.

One seller goes further and says many Kohler French curve toilets don't work with any of Kohler's own bidet seats. So a Kohler-branded bidet is not automatically the one that fits your Kohler toilet.

Kohler toilets that are usually easy

Kohler's everyday two-piece families, the ones in most homes and rentals, have a separate tank and a flat area behind the seat. Kohler's compatibility grid lists the Cimarron family, for example, as working with many of its bidet products. Two-piece toilets like the Highline, Wellworth and Memoirs two-piece models are built the standard way, but measure anyway: models within a family differ.

For any two-piece Kohler, the usual checks apply. Our guide to whether bidet attachments fit all toilets gives the three measurements: bolt spacing, tank gap and bowl length.

Kohler's own fit grid

Kohler publishes a PDF compatibility guide for its bidet seats and its PureWash bidet products. It lists Kohler toilet families down the side and its bidet models across the top, with a yes or no in each box. If you're looking at a Kohler-made bidet, it's the first place to check. If you're looking at another brand's attachment, it still helps: a toilet that Kohler marks "no" for its own slim attachments is a warning sign for any attachment.

Kohler's own attachment: the PureWash M100

Kohler makes a non-electric bidet attachment, the PureWash M100 (K-22860). Kohler describes it as giving bidet function to most toilet seats. Retailers describe it as made for most elongated toilets, and some list it for elongated or round. Listed prices we saw ran from about $30 to $75 depending on the store.

It goes on the same way as any attachment: under the seat, through the seat bolts, with a T-adapter on the tank's water line. It faces the same limit too: it needs a flat area behind the bolts. On a Rialto or San Raphael, the brand name on the box doesn't change the shape of the bowl.

Other brands' attachments on a Kohler

Most attachments say they fit "most toilets, including Kohler, American Standard and TOTO". For a two-piece Kohler with a flat deck that's usually true, because Kohler's two-piece bowls use the standard US seat-bolt layout and the standard 7/8 inch tank inlet thread that US T-adapters are made for.

Where Kohlers differ is the space at the back:

Tight space behind one-piece toilets. One buyer of an attachment on a San Raphael elongated one-piece reported it worked, but needed a different water adapter because of the tight space behind the toilet. One-piece tanks often sit low, close to the wall valve, with little room for the T. Our T-valve fit guide covers the fixes.
Rigid supply lines. Older Kohler installs often have a chrome rigid pipe from the wall to the tank. The T adds about an inch, so the pipe won't reach. Swap it for a flexible braided supply line.
Skirted Kohler toilets may hide the inlet behind the side. Plan the hose route before buying.

Kohler seats and bidet attachments

An attachment sits under your seat, so the seat's hardware matters as much as the bowl.

Quick-release and ReadyLatch-style seats lift off a bracket that bolts down. The bracket bolts through the attachment's plate. Check the seat clicks fully back onto the bracket afterwards.
Quiet-Close (soft-close) seats work like any soft-close seat. The lid's resting angle can change a little because the back sits higher.
Grip-Tight style bumpers under Kohler seats are meant to stop shifting. With an attachment, the back of the seat is higher, so the front bumpers may no longer touch evenly; extra stick-on bumpers level it. Our page on what to do when a bidet attachment doesn't fit covers the wobble fix.
Top-fix bolts (tightened from above) are common on one-piece toilets. A plate under the seat can stop the rubber anchor gripping; a longer top-fix kit solves it.

A five-minute fit check for any Kohler

Find the model number inside the tank. Look it up: one-piece or two-piece? French Curve seat?
Lift the seat. Is there a flat ledge of about 1.5 inches behind the bolts?
Measure bolt to bolt, and bolts to the front of the rim (18 inches or more is elongated).
Look under the tank: flexible hose or rigid pipe? Room for a T between the tank and the wall valve?
Note the seat type: bolt-down, quick-release, top-fix.
Take two photos: from above with the seat up, and of the water pipe.

Send the model number, those numbers and the photos to any seller, and you'll get a real yes or no. When ours goes on sale, we'll ask for exactly that before you pay. Meanwhile, find out which bathroom god you are with the ASSJET quiz.

If your Kohler won't take an attachment

A bidet seat made for the model. A few third-party seats with narrow, rounded backs are sold for specific Kohler one-pieces. Fit is model by model, and most need an outlet. See bidet attachment vs seat.
A handheld sprayer. It hangs on the wall or the tank and never touches the bowl, so the curve doesn't matter.
A different toilet. One bidet seller estimates a standard two-piece elongated toilet at under $200, about $250 to $300 with a plumber, which then takes almost any bidet. Not an option in a rental.

FAQ

Do bidet attachments fit Kohler toilets?

Most two-piece Kohler toilets, yes. Some one-piece models with a French curve, like the Rialto and San Raphael, usually don't.

Where is the model number on a Kohler toilet?

Inside the tank, on the back wall, molded into the china or stamped in ink. On a two-piece toilet that's the tank's number; the bowl's is under its back flange.

Does Kohler make a bidet attachment?

Yes, the PureWash M100 (K-22860), a non-electric attachment that goes under your existing seat. It still needs a flat area behind the seat bolts.

Will a Kohler bidet seat fit every Kohler toilet?

No. Kohler's own compatibility guide marks some toilet families no for some of its seats, and sellers say many Kohler French curve toilets don't take Kohler bidet seats.

My Kohler is one-piece. Is it hopeless?

No. Many one-piece toilets have a flat ledge behind the bolts. Check for that ledge and for room under the tank for the T-adapter.

More fit help: a bidet that fits an elongated toilet, and all our answers in the guides.

Sources

Bidet toilet seat and PureWash compatibility guide (24-3301), Kohler. https://kohler.com/content/dam/kohler-com-NA/Lifestyle/PDP-PDF/bidet-toilet-seat-f-and-b-compatibility-guide-24-3301-0924.pdf
Rialto one-piece round-front toilet with French Curve seat (K-3386), Kohler. https://www.kohler.com/en/products/toilets/shop-toilets/rialto-one-piece-round-front-1-6-gpf-toilet-with-rim-jet-flush-technology-left-hand-trip-lever-and-french-curve-toilet-seat-3386
San Raphael one-piece round-front toilet with French Curve seat (K-3467), Kohler. https://www.kohler.com/en/products/toilets/shop-toilets/san-raphael-one-piece-round-front-1-6-gpf-toilet-with-ingenium-flush-technology-left-hand-trip-lever-concealed-trapway-and-french-curve-toilet-seat-3467
What Bidet Toilet Seats Will Fit My Kohler Rialto Toilet?, BidetKing. https://bidetking.com/blog/what-bidet-toilet-seats-will-fit-my-kohler-rialto-toilet/
Identifying your toilet model (Kohler model number locations), Guaranteed Parts. https://guaranteedparts.com/picture_library/Kohler/find-model-number-location/identifying-your-toilet-model.pdf
Kohler PureWash M100 Toilet Seat Bidet Attachment (K-22860), First Supply. https://firstsupply.com/Product/K22860WHT