Fit guide
Bidet seats for French curve toilets: how to check the fit before you buy
French curve toilets look great and are a pain to fit. The curve that makes them pretty takes away the room a bidet seat needs at the back. Some seats fit, many do not, and the only honest way to know is to measure your toilet. Here is how we check it.
The short answer
- No bidet seat fits every French curve toilet, and we do not know of any published measurement that proves one does.
- The number that decides it is the room from the centre of the seat bolt holes straight back to the tank or toilet body.
- Send us your toilet model number, three measurements and two photos. We tell you yes, no, or which seat we would pick instead, before you order.
- The seat we look at first is the Infinity Eaze-Z3. Infinity says it can fit French curve toilets. It still needs a check.
On this page
What a French curve toilet is
On most toilets the tank sits behind the bowl and drops straight down. There is a flat shelf of porcelain between the seat bolt holes and the tank, and that is where a bidet seat’s back housing sits.
On a French curve toilet the tank or the body of the toilet sweeps forward in a curve and blends into the back of the bowl. Many are one-piece toilets with a low tank. Kohler, American Standard and other brands have made them for years, and you find them in a lot of older homes and higher-end bathrooms.
Why bidet seats struggle with them
An electric bidet seat keeps its water heater, pump and electronics in a housing at the back, right over the bolt holes. A plain toilet seat only needs a hinge there. When the curve comes forward, the housing hits the porcelain before the seat lines up with the bowl.
Two other things can go wrong on these toilets:
- The bolt holes can be hard to reach from below, which makes the mounting plate fiddly to tighten.
- The water shut-off valve can be tucked behind the curve, which makes the T-valve install awkward.
None of this means you cannot have a bidet seat. It means you need to check before you buy.
The three measurements
- A. Bowl length: from the centre line of the bolt holes to the front of the rim. About 18.5 inches is elongated, about 16.5 inches is round.
- B. Bolt spacing: the distance between the two bolt holes. The standard is 5.5 inches (140 mm), and the Infinity Eaze-Z3 mounting plate only fits that spacing.1
- C. Room behind the bolts: measure straight back from the centre of a bolt hole to the closest point of the tank or toilet body. On a French curve toilet the closest point is often low down, where the curve meets the bowl. If you get less than about 1.5 inches, do not order anything until we have seen photos.
A tip on measurement C
Hold the tape level and slide it back until it touches porcelain. Do not measure along the curve. If the curve changes a lot with height, measure at the rim and again about 2 inches up, and send us both numbers.
Two photos and a model number
Numbers help, but photos and the model number are what let us give you a firm answer.
- Model number. Look for a sticker or stamp inside the tank (lift the lid off), on the underside of the tank lid, or on the back of the toilet near the floor.
- Side photo. Stand beside the toilet and get the whole thing in the shot, from the tank to the front of the bowl.
- Bolt-hole photo. Lift or remove the old seat and shoot down at the back of the bowl, so we can see the bolt holes and the tank behind them. A tape measure in the photo helps.
Send it all through the free fit check on the Eaze-Z3 page, or email [email protected]. When you give us the model number, we look up that toilet’s own specs before we answer.
Which seats we look at first
We only list a seat here when we have a reason to. This list is short on purpose.
Infinity Eaze-Z3
Infinity, the maker, says the Eaze-Z3 can fit French curve toilets. It comes in round and elongated, needs 5.5 inch bolt spacing, and the mounting plate is bolted down first, with the seat sliding onto it afterwards.1 It still needs measurement C checked. It is also covered by our 60-day trial, but the seat must come back sanitized in its original box and packaging, which is another reason to check first.2
Kohler toilets
Kohler publishes a compatibility guide for its own bidet seats. If you have a Kohler French curve toilet, send us the model number and we check it against that guide as well. If Kohler lists its own seat for your toilet, we can supply the Kohler C3-230.
Not on this list: every other seat. That does not mean they never fit. It means we will not tell you they fit until we have seen your toilet.
Video: what the curve does
This video explains what a French curve is and why it makes fitting a bidet seat hard. It was recorded in 2020 by Many Bidets, our Eaze-Z3 partner, before the Eaze-Z3 existed, so it does not show the Eaze-Z3. Use the toilet list in its description as a starting point only. Your own measurements decide the fit.
Play the French curve video
Toiletland partnered with Many Bidets to help bring the Eaze-Z3 to Canada. The video opens on YouTube only after you choose to play it.
Frequently asked questions
How do I know if my toilet has a French curve?
Look at the toilet from the side. If the tank or body curves forward and blends into the back of the bowl, instead of dropping straight down behind a flat shelf, it is a French curve. Many are one-piece toilets with a low tank.
Is there a bidet seat that fits every French curve toilet?
No. The curve is different on every model, and we do not know of any published measurement that proves a seat fits them all. That is why we check each toilet by model number, measurements and photos.
Which measurement matters most?
The room from the centre of the seat bolt holes straight back to the closest point of the tank or toilet body. If it is under about 1.5 inches, send us photos before you order anything.
Can I cut or modify the mounting plate to make it fit?
We do not recommend it. Infinity’s manual says not to alter the unit, and its warranty does not cover damage from alteration.
Where do I find my toilet model number?
Look inside the tank with the lid off, on the underside of the tank lid, or on the back of the toilet near the floor. It is usually a sticker or a stamp in the porcelain.
What if I order and it does not fit?
The Infinity Eaze-Z3 is covered by our 60-day trial, and Toiletland provides a prepaid return label, but the seat has to come back sanitized, complete, and in its original box and packaging. A five-minute fit check up front saves that hassle.
Ready to check your toilet?
Measure A, B and C, take two photos, and find the model number. We will do the rest.
Sources
- Infinity Eaze z3 instruction manual (models Z3-EW and Z3-RW), Infinity Bidet. Installation page 7, detachment page 17, warranty page 21.
- Shipping and Returns: 60-day trial terms, Toiletland Canada
- Bidet Seats For French Curve Toilets, Many Bidets, 2020