Tankless Toilet with Bidet: The Ultimate Guide

A tankless toilet

Today’s article looks at how bidets can be installed on tankless toilets. Whether you have a wall-hung or flushometer toilet, the one common denominator is that tankless toilets don’t provide any external access to the water supply connection.

There is a workaround, and to do it, you’ll need the best bidet for a tankless toilet (Amazon link). It’s a dual-temperature non-electric bidet, so it comes with the needed parts to bypass the toilet shutoff valve.

For those in a rush, jump to the section on how to install a bidet on a tankless toilet, method 1 (see table of contents). In short, you’ll follow the directions for installing a warm water bidet attachment but do so on the cold water shutoff valve under the sink. 

Dual temperature non-electric bidets come with a 9-10 foot hose and a 3/8″ T-adapter, both of which are needed. The hose will run from the alternative cold water shutoff valve to the cold water inlet on the bidet. Finally, the hot water cap will be put on the hot water inlet. If you want warm water, you can use double the parts.

We’ll be covering different types of tankless toilets from the truly tankless (the flushometer and pressurized kind) to the concealed cistern kind (wall-hung flush tank toilets).

Can You Install a Bidet on a Tankless Toilet?

Bidets can be installed on tankless toilets. Special conversion kits exist that allow connection to the water supply valves beneath the bathroom sink. Also, adapters are available that attach the supply hose directly to the faucet. Finally, you can have a plumber install a new shutoff valve.

Each method has its pros and cons which we’ll be covering in detail.

Most manufacturers claim that their bidets are compatible with all kinds of toilets. What they mean is that their bidets fit both one-piece and two-piece commodes and are available for both round and elongated toilets.

And it’s not their fault. Toilets have undergone more changes over the past 15 years than any other bathroom fixture. It’s nigh impossible to make a bidet that’s compatible with every possible toilet design.

Depending on your current setup, you may need a very specific bidet or special adapters or hoses.

True Tankless Toilets (Flushometer)

Unlike toilets that work off gravity from the tank, flush valve toilets (flushometers) operate without a tank. This type of toilet makes use of the higher pressure offered by the larger pipes present in the buildings in which the toilets are used.

It’s usually larger buildings that have sufficient water pressure for this kind of setup, which is why flushometers are more common in public restrooms than residential properties. The extra pressure provides a large gush of water quickly enough to flush out the toilet’s contents.

They can be both floor and wall-mounted.

These look like standalone bidets but they’re crude drawings of tankless toilest.

Most bidets, as they come new in the box, won’t be compatible with this type of toilet. Bidets come with a T-connector or junction that’s meant to be connected to the threaded shank that extends down from the toilet tank.

The traditional setup: a T-connector sending water to the toilet tank and bidet.

The adapter allows water from the shutoff valve to be routed to both the tank and the bidet.

On flushometer toilets, there’s nothing to attach the adapter to.

Tankless toilets are typically installed in bathrooms that don’t have a toilet shutoff valve. With a flushometer, the only access you get to the water is when it enters the bowl. But with the help of certain adapters, you can get access to other shutoff valves in the bathroom.

If you have one of these, consult the section below on how to install bidets on a tankless toilet.

Pressure-Assisted Tankless Toilets

The other main category of truly tankless toilets is the pressure-assisted kind. These use pressure to replace gravity, so unlike the flushometers, they don’t require a building to have high-powered plumbing.

I’m sure other tankless flushing technologies exist. The industry is evolving all the time and manufacturers probably use a number of technologies to ditch the tank. But the flushometer and pressure-assisted mechanisms are the two main varieties.

Not every toilet that uses pressure is tankless. In some cases, the flushing mechanism (usually a Flushmate) is housed in a traditional toilet tank.

But modern high-tech toilets (even those without bidet function) are often completely without a tank. The tankless pressure-assisted design is typical for floor-mounted bidet-toilet combos (the commodes that are originally built with bidet technology).

So, the technology that allows for tankless flushing without high-powered plumbing is fairly common in advanced toilets, even those without a bidet.

I’d imagine that some reading this article have this type of toilet and want to know how to attach a bidet. The main issue with installing a bidet on one of these toilets is that the bathrooms in which they’re designed to be used lack toilet shutoff valves. If the bathroom originally had a flush tank toilet, then this won’t be an issue.

Another set of problems you can encounter with this kind has to do with design. Is the structure of the commode compatible with bidets on the market? High-tech toilets not only come with rare technology but odd designs and dimensions.

This means that components may be too long or not long enough, or that holes won’t line up, etc. So, if you have one of these, make sure to read the section installation challenges.

Concealed Cistern (Behind the Wall Tanks)

These are typically referred to as wall-hung toilets. Flushometer toilets can be wall hung too, so I’m referring to these as toilets with behind-the-wall tanks.

A concealed cistern wall-hung toilet.

The wall-hung setup is a popular design for both residential and public restrooms. For residential properties, they provide a nice ultra-modern minimalist appearance. Public restrooms use them because they’re easier to clean and resistant to vandalism.

Bidets can be installed on wall-hung flush tank toilets, either by having a plumber install a new shutoff valve or by using the valves beneath the sink. Like with flushometer toilets, they don’t provide external access to the toilet’s water supply connection, so adjustments must be made.

This type of toilet has its benefits. I mean, they do look snazzy.

But to get that nice clean minimalist appearance, you give up access to the water supply, the tank, drainage hole, and flushing mechanism which are all hidden behind the wall. Additionally, bathrooms designed to have wall-hung toilets don’t have toilet shutoff valves at all.

The installation instructions that come with most bidets have the user locate the water shutoff and toilet fill valves on the left-hand side of the toilet (when facing it).  

For info on how to deal with the issue, see the next section.

How to Install a Bidet on a Tankless Toilet

Method 1: Using an Alternative Shutoff Valve

The easiest way to use this method is to get a warm water bidet attachment like the LUXE Neo 320. It comes with a 10 foot hose and a 3/8 inch T-adaper. Most bidets come with a short hose and a 7/8″ adapter.

After you’ve attached the bidet to the toilet, attach the supply hose as described below.

Of course, you’ll want to consult the installation manual for your specific model, but here are broad strokes.

Step 1: Route the Supply Hose to the Coldwater Shutoff Valve Beneath the Bathroom Sink

Run the hose from the bidet to beneath the sink under the shutoff valves. You’re just making sure the hose is long enough at this point and if a hole needs to be drilled in the vanity (if you have one). Pedestal sinks are ideal for this method.

I recommend the Neo 320 but most warm water bidet attachments should do the trick. If you have a Tushy Classic, they make a conversion kit meant specifically for tankless toilets. It comes with two hoses and all the right connections. Finally, if you already have a bidet, check with the manufacturer to see if they have a 9-10 foot hose.

When it comes time to hook it up, make sure to attach the hose to the cold-water valve. I.e., if not sourcing water from both valves (with two hoses) then cold is the way to go—otherwise, you get just hot water.

Step 2: Turn the Cold Water Valve Off

Locate the cold-water valve beneath the sink and shut it off by turning it clockwise.

Step 3: Disconnect the Cold Water Sink Supply Hose

Disconnect the flexible steel hose that runs from the water supply valve to the faucet. Do this by turning it counterclockwise.

Step 4: Attach a 3/8″ T-Connector to the Valve

Attach a 3/8″ T-connector to the cold water shutoff valve where the hose was threaded on. Turn clockwise with your hand then with a wrench (don’t overtighten).

If you have a warm water bidet attachment, it’ll be the “hot water T-adapter” (you won’t be using the “cold water T-adapter”).

If you don’t have a warm water bidet attachment, get a T-adapter for skirted toilets. First, try with the manufacturer of your bidet, and if they don’t have one check with Bidet King and other sources. If you go this route, you’ll need to find a hose that’s long enough and fits the bidet inlet and shutoff valve.

Make sure all three dimensions are correct:

Step 5: Connect the Cold Water Sink Supply Hose to the T-Adapter

Thread the hose to the top of the adapter, turning it clockwise with your hand followed by a wrench.

Step 6: Attach the Bidet Hose

Finally, attach one end of the bidet hose to the T-connector and the other to the bidet (if the latter hasn’t been done already).

It should look like this.

You’ll need an extra hose and T-valve, but if you want warm water, you can repeat the above steps for the hot water shutoff valve.

At this time, you should be able to go ahead and turn the water back on. Make sure the O-rings are in place or it’ll leak everywhere.

Pros and Cons of Method 1


  • Less hassle long term. No having to constantly fiddle with the bidet every time you want to use it. By hooking the supply hose up to the sink’s plumbing instead of the faucet (the next method), you won’t have to connect it every time you want to use it.
  • Warm water capability w/out electricity. For those who are disappointed that they’ll have to go through the extra trouble of using this fancy hookup, keep in mind that warm water is usually limited to electric bidets. By installing your bidet into the home’s water supply lines, you can get the benefit of warm water with less expensive non-electric bidets.


  • It may require altering the property. If you have a vanity that gets in the way (and it can’t be moved), then you may need to drill a hole for the supply hoses to go through—kind of like putting TV cords through an entertainment center. Making permanent alterations to the property is usually out of the question for renters unless permission is granted first. It would be an eyesore, but running the supply hose through the front of the vanity is another option.
  • You may need extra parts. For those who have a bidet, you’ll have to get extra parts. Tushy makes it easy with their conversion kit. They’re not expensive, but most bidets that hook directly to the faucet come with the needed adapters. The conversion kit comes separately.

Method 2: Hooking the Bidet to the Faucet

This method sources water straight from the faucet. By connecting to the faucet, you get full temperature control with a single supply hose. You can get the full range of temperature because the warm and cold-water merge before entering the hose.

It’s a somewhat common method even on flush tank toilets because it allows for warm water flow on non-electric bidets. It’s also great for short-term stays (Airbnb and hotels) when you can’t install anything.

For this method, you’ll probably want to get a handheld bidet made for this purpose.

For those who already have a bidet, you can reach out to the manufacturer and ask if they have an adapter that will work for your situation. They’ll probably have you send a photo of your faucet along with its dimensions to see if they have one that fits.

Pros and Cons of Method 2


  • Easy installation. The initial installation mostly just involves placing the bidet on your existing toilet. Unlike with method 1, you don’t have to worry about shutoff valves and T-connectors.
  • Some bidets come with the needed connections. Just look for a sprayer advertised as a faucet bidet.
  • No permanent alterations to the property. Hooking straight up to the sink, you’ll never have to drill through any vanities. Again, this isn’t always a problem with method 1.
  • Full temperature control with the faucet.


  • Connecting the bidet with each use. You don’t have to but the hose tends to get in the way otherwise. The only way around this would be if you have two sinks and one is unoccupied. In that case, you could have a dedicated bidet sink. This is impractical for most because bathrooms with two sinks are usually shared. I.e., not many people have a spare sink.

Potential Challenges with Both Methods

These challenges apply to both installation methods.

If your sink and toilet are far apart (> 9 ft or 2.7 m apart) – In such a case, the hose may not be long enough to reach the sink shutoff valves or faucet.

If your toilet and sink are on opposite sides of the room – For either method, you’ll need your toilet and sink to be on the same side of the bathroom. Even if the hose were long enough, you don’t want it to be draped across the floor ready to trip anyone who walks by.

Method 3: Consult a Plumber to Install a Shutoff Valve

Finally, in some situations, you can get a plumber to install a new shutoff valve next to the toilet. This is probably only practical when remodeling or building a new property.

If remodeling a bathroom, ask the plumber if they can put a shutoff valve next to the toilet in the same way they would for a floor-mounted flush tank toilet.

This may or may not be feasible depending on your current bathroom setup, but it’s worth a try. If designing a new property, you can design the bathroom any way you want so just ask for the shutoff valve.

Other Installation Challenges

Odd Toilet Shapes and Sizes

As mentioned earlier, toilets have undergone so many changes over the last decade and a half. So, new problems can pop up with any new toilet variation.

Manufacturers have taken into account the main ways in which toilets differ these days, but it’s hard to plan for everything.

They usually focus on the round vs. elongated distinction and variations in bolt hole widths. Most bidets come in two versions, one for round toilets and the other for elongated.

In North America, 5.5” is the standard distance between bolt holes on the back of the rim, but it can vary. So, manufacturers include a mounting bracket with their bidets to accommodate different widths.

But what about oddly shaped toilets?

Flushometer toilets, while tankless, tend to have a traditional design when it comes to the rest of the commode (the bowl or basin). But some of the newer tankless and wall-hung toilets are meant to go with ultra-modern bathrooms. Being non-traditional, modern toilets can take on a range of shapes and dimensions.

I’ve seen some in the shape of a square (like a box) and others a sphere. I’ve even seen one that looks like some kind of droid out of a Star Wars film.

Don’t get me wrong, most toilets—even the newer designs—have more of a traditional look. But the odd shapes are more common with newer models.

A mismatch between a bidet and toilet may just result in an awkward appearance, but differences in some dimensions can interfere with the installation. The rear of the toilet may be too wide or there may be something in the way. Or, as we’ll discuss soon, the bolt hole width may be incompatible.

This compatibility issue isn’t limited to tankless toilets. For example, some toilets have French curves that can get in the way of the mounting bracket. Also, some one-piece toilets can be too wide in the back where the basin flairs out to mee the tank.

Skirted Toilets

For this type of design, make sure to read the article on how to install a bidet on a skirted toilet.

This is an easy fix but something to keep in mind especially if you have a wall-hung toilet. The vast majority of wall-hung toilets are skirted—this goes for both the truly tankless kind (flushometer and pressurized) and concealed cistern toilets that have a tank hidden behind the wall.

This is related to the above (atypical designs) and applies to any skirted toilet (tank or no tank). I bring it up here because, like the tankless look, the skirted design is common on newer toilets that are meant to go with modern bathrooms.

Skirted toilets are designed to conceal the commode’s innards like trapway (that curvy S-shaped pipe). This gives the toilet a nice sleek look. Bidets are meant to be mounted to the toilet using the same bolt holes that attach the existing seat.

Bidet seats replace the entire seat/lid combo on the current toilet. Bidet attachments are fixed underneath the current seat but don’t replace anything.

Anyway, non-skirted toilets provide access to the underside of the bolts (where the nuts are threaded on) allowing you to attach and re-attach them any time.

To work around this, skirted toilets come with top mounting bolts. They’re often compatible with bidets, but not always. If not, you’ll need to get new top mounting bolts of the appropriate size.

The other common issue with skirted toilets won’t apply. Namely, lack of access to the fill valve.

Odd Bolt Hole Widths

Yet another design issue. This tends not to be an issue with flushometer toilets.

Again, 5.5 inches is the standard distance between toilet seat bolt holes in North America. As mentioned, the distance can vary so bidets come with adjustable mounting brackets to accommodate the typical range in lengths—usually 5-7 inches.

Wall-hung toilets can have bolt holes several inches outside the normal range—some reaching almost twice the average distance. If you have bolt holes far outside the range of what mounting brackets can accommodate, then you may want to go with a handheld sprayer. Either that or use some creativity to engineer a workaround.

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