Bidet Seat Compatibility: Checking an Existing Toilet

A bidet seat is the fastest smart bathroom upgrade available, because the ceramic stays where it is. No drain work, no rough-in question, no floor repair. The trade-off is that the existing pan now sets the constraints, and pans vary far more than catalogues imply.

Five measurements and one photograph answer the compatibility question. This is the survey we ask for before a sample ships.

The five measurements

Our T1 installation guide states the required clearances directly:

Check	Requirement
Front of bowl to tank	Greater than 49 cm
Tank to mounting hole	Greater than 2.8 cm
Mounting-hole centre distance	13.5–18 cm
Nearby power socket	Within approximately 1.5 m
Nearby water inlet valve	Within approximately 0.5 m

The first three describe the ceramic. The last two describe the room, and they are the two most often skipped — a seat that fits perfectly on a pan with no reachable outlet is still an unusable installation, and an extension cord is not an acceptable remedy on a mains-heated appliance in a wet room.

Take the mounting-hole measurement centre to centre, with the old seat removed if possible. If the existing seat is still fitted, measure between the visible bolt caps and note that the reading is approximate.

Tank shape: what adapts and what does not

The supplied T1 fitment guide identifies straight, slightly forward and slightly backward water-tank shapes as adaptable. Square water-tank toilets and some irregular ceramic profiles are not suitable.

The reason is geometric rather than commercial. A bidet seat needs the hinge housing to sit flat behind the bolt holes and needs the lid to clear the tank face through its full swing. A square tank with a vertical face at the rear of the bowl leaves no room for the housing, and a strongly sloped or sculpted tank changes the angle at which the seat sits.

When the shape is ambiguous — one-piece designs, skirted pans, and heavily styled European ceramics are the usual candidates — send a side-on photograph of the actual toilet. That single image resolves the question faster than any written description, and it is the first thing our technical team asks for.

Bowl shape has to match the seat

Seats are built to a bowl profile. The B04 is documented as an elongated seat with an overall size of 513 × 396 × 103 mm and a seat width of 374 mm in its dimension drawing; with the lid open it needs 534 mm of length and 555 mm of height clearance. A round bowl is a different reference, not a smaller version of the same product.

The T1 is a V-shaped seat measuring 495 × 435 × 115 mm, designed as an upgrade format for the tank-type pans described above.

Both are light — 3.9 kg for the T1 and 3.3 kg for the B04 — which is why a single installer can complete the change in one visit once the fit is confirmed.

The plumbing and electrical connection

The connection work is straightforward but has fixed requirements:

• Water. The B04 takes its supply from the side, with a 13.1 mm inlet diameter, and ships with a tee-junction component and inlet hose so the existing fill line can be shared. Its working pressure is documented from 0.07 MPa dynamic to 0.75 MPa static, with 4–35 °C supply water.
• Mounting. The B04 includes a fast mounting plate with an installation adjustment range of 125–190 mm, along with adjustment sheets and fixings. The T1 ships with a fixing plate, adjustment pieces, bolts and nuts, inlet pipe assembly and filter.
• Electrical. Both are 110V-class configurations for North American supply. Confirm a grounded, GFCI-protected outlet within cord reach — the voltage and grounding guide covers the electrical requirements in full.

Surveying a bulk retrofit

Hotels and multi-unit residential buildings are rarely uniform. A property refurbished in phases can easily have three different pans across its floors, and a single sample approval on one of them is not evidence for the other two.

A workable survey method for a property:

1. Walk the floors and group rooms by pan type, photographing one example of each.
2. Take the five measurements once per group, not once per room.
3. Note outlet position and valve position per group — these often differ by stack rather than by room.
4. Sample one seat per distinct group, and approve per group.
5. Then order by group quantity, which also gives your installer a per-floor pick list.

For properties where more than about a third of rooms fail the checklist, an integrated smart toilet replacement is usually the cheaper path once installer time is counted — the smart toilet category covers the integrated options, and the 300 mm vs 400 mm rough-in guide covers the drain measurement that decides which integrated model fits. Our hotel programme and remodeler support pages cover how those two routes are usually mixed in one project.

Before you order

Send the five measurements, a side-on photograph of the pan, the outlet and valve positions, and the room count per pan type. We will confirm the fit, flag any group that needs an integrated unit instead, and quote by group.

Full specifications for both seats are on the T1 and B04 records, the seat category page compares the two formats, and manuals are available in technical downloads. Answers to common retrofit questions are in the procurement FAQ. If a pan does not match anything in this guide, send the photograph to our technical team and we will tell you plainly whether it can be fitted.