A tankless intelligent toilet takes the bidet, heated seat, dryer and flush out of separate components and puts them into one floor-standing body. The Kohler Floor Standing Intelligent Bidet Toilet (42573A-W3) is that type of unit. It also brings site requirements a normal close-coupled suite doesn't have: a powered outlet, a minimum mains pressure, a fixed set-out range and a backflow question to settle with the local authority.
This guide covers what to check before ordering one, so the rough-in is right the first time.
What "tankless" actually means for the install
There is no cistern, either close-coupled or in a wall frame. The 42573A-W3 flushes off mains pressure through an internal valve, using a 4.5L full / 3L half flush with Kohler's Revolution 360 rim wash. For the build that means:
- No in-wall cistern frame to buy, frame up, line and access. On a renovation that's a real saving in carpentry and sheeting compared with a concealed-cistern wall-hung pan.
- A low, clean profile against the wall, which is why these units suit ensuites where a visible cistern looks out of place.
- Mains pressure becomes a design input. A cistern stores water so it doesn't care much about supply pressure. A tankless unit does.
Pre-install checklist
1. Water pressure: 80kPa minimum, 500kPa maximum
The listing specifies an inlet pressure of 80kPa minimum and 500kPa maximum. The low end matters on tank-fed or gravity-fed supplies, upper-floor bathrooms on weak mains, and some rainwater/pump setups. The high end matters more often than people expect: many Australian streets run above 500kPa, and AS/NZS 3500.1 already caps pressure inside a building at 500kPa at any outlet. If the property doesn't already have a pressure limiting or reducing valve, fit one at the meter. Our Rinox PRV comparison covers the options.
Inlet water temperature must sit between 3 and 35°C, so it's a cold-water connection only. The unit heats its own wash water.
2. Power: dedicated 220–240V outlet with RCD protection
The seat heater, dryer, wash pump and auto lid all run on mains power. The listing calls for a dedicated 220–240V, 50Hz power point with RCD protection, and the unit is rated IPX4. Get the electrician to place the outlet before the wall is sheeted and tiled, positioned to suit the unit's cord exit, not wherever is convenient. The electrical connection must be done by a licensed electrician.
3. Set-out: 95–110mm S-trap or 180mm P-trap
- S-trap (floor waste): 95–110mm set-out from the finished wall to the centre of the outlet. A Vario pan connector is supplied for this.
- P-trap (wall waste): 180mm set-out. The P-trap connector is not supplied, so order one separately.
The 95–110mm S-trap range is narrower than many standard pans. On a replacement job, measure the existing set-out to the finished tile face before ordering. A 140mm or 160mm existing set-out won't suit without moving the waste.
4. Backflow protection
Any bidet connects drinking water to a fixture that handles waste, so backflow protection is a compliance issue, not an optional extra. According to the listing, the 42573A-W3's bidet seat has an integral air gap (AS 2845.2, per the manufacturer's spec sheet). The listing also recommends checking with the local water authority whether an additional RPZD is needed on the supply. Requirements differ between authorities, so make that call before the rough-in, not at final inspection. Our dual check valve guide explains hazard ratings and where each device type fits.
5. User weight and supply fittings
Maximum user weight is 150kg. In the box you get the toilet and remote, an angle valve with removable filter, braided stainless supply hoses, the Vario S-trap connector and floor fixing hardware. The filter in the angle valve is worth showing the client, since a blocked filter is a common cause of weak wash spray on mains-fed bidets.
What the client gets day to day
- Foot sensor at the base opens and closes the lid and seat and triggers the flush, so it's hands-free.
- Pre-use bowl mist to reduce waste sticking, and a plasma sterilisation cycle on the bowl after use (both manufacturer-described features).
- Rear and front warm-water wash with oscillating spray, adjustable for temperature, volume and nozzle position.
- Heated seat and warm-air dryer, automatic deodorising, a night light and an energy-saving mode, all operated from the included remote.
Tankless floor-standing vs an in-tank smart suite
If the job can't meet the 80kPa minimum, or the budget is tighter, the Johnson Suisse Wall Faced Rimless Smart Toilet Suite is the alternative to consider. It's a different design with an integrated in-tank cistern, so a stored flush. Its listing shows WELS 4 Star (4.6/2.9L), UV nozzle sterilisation, a smart dial instead of a remote, and an integral high-hazard backflow device it states needs no additional RPZ.
| Kohler 42573A-W3 | Johnson Suisse smart suite | |
|---|---|---|
| Cistern | None (tankless, mains-flushed) | Integrated in-tank |
| Flush | 4.5L / 3L, Revolution 360 | 4.6L / 2.9L, rimless |
| Hands-free lid & flush | Yes, foot sensor | No |
| Control | Remote | Integrated smart dial |
| Backflow (per listing) | Integral air gap; check if RPZD needed | Integral high-hazard device; no RPZ stated |
| Price | $4,100 | $2,499 |
Choose the Kohler when the client wants the hands-free auto lid and flush and the tankless profile, and the site has adequate mains pressure. Choose an in-tank suite when pressure is marginal or budget matters more. If the client only wants a bidet wash and isn't replacing the toilet, a retrofit bidet set is a far cheaper option.
Browse the full range in our Bidets collection. Availability on the 42573A-W3 can vary, so contact the PSA team to confirm lead time before you lock in the install date.
Frequently Asked Questions
Does a tankless bidet toilet work on low water pressure?
Only down to its rated minimum. The Kohler 42573A-W3 needs at least 80kPa at the inlet and no more than 500kPa. Below 80kPa it can't flush properly from mains, so a tank-fed or very low-pressure supply needs an in-tank suite or a booster.
Do I need a power point behind the toilet?
Yes. It needs a dedicated 220–240V outlet with RCD protection, installed by a licensed electrician. Plan the outlet position before the wall is tiled.
Will it fit my existing toilet waste?
It suits an S-trap set-out of 95–110mm (connector supplied) or a 180mm P-trap set-out (connector not supplied). Measure from the finished wall to the centre of the waste before ordering.
Is an RPZD required for a bidet toilet?
The 42573A-W3 has an integral air gap in the bidet seat, but the manufacturer recommends checking with your local water authority whether an additional RPZD is needed on the supply. Requirements vary, so confirm before rough-in.