The art of the in-wall carrier system

By Denise Deveau

More and more commercial toilet installations in North America are using in-wall carrier systems, but the path to hidden plumbing is not exactly new for those with a well-stamped passport.

Tim Schmidt, product manager for flushing and drainage with Viega, says the wall-hung toilet trend is actually pretty old-school for anyone from Europe. “The technology has been developing since the 1960s. It began trending in North American in the late 1990s,” he says. “This is the next evolution in toilets. They save space and water usage, and improve hygiene.”

Dan Walker, Sloan brand manager at Dobbin Sales, says in-wall systems are the preferred installation approach in new construction projects. “All new office towers are using concealed valves. It’s a cleaner look.”

They are not typically used in retrofits since you have to start from zero, he adds. “The only way it would work for retrofits is if you are gutting the washrooms and rebuilding them. But typically they would prefer not to exchange the piping.”

One of the biggest reasons for going the in-wall route is design choice, says Tony D’Amato, senior product manager with American Standard Brands.

“A lot of designers want everything hidden in commercial spaces because it’s aesthetically pleasing and eliminates clutter.”

Another compelling reason is vandalism, he explains. “They’re hiding the flush valves in the walls so they can’t be damaged,” says D’Amato. “You need an electrician and a plumber, while an exposed system just needs a plumber who can do the job in 15 minutes rather than an hour to do a concealed valve, but it pays for itself in cost savings from reduced vandalism.”

“There are even specially designed flush plates with tamper-free features that you can’t pry off with screwdrivers,” Schmidt notes.


Obviously, the installation is not the same as a floor-mount two-piece toilet, but it isn’t as difficult as one might think, says Schmidt.

“The difference is you’re moving that connection of the waste line inside the wall. But outside of that, the functionality and how it’s installed is not that difficult or different,” he says. “You connect the carrier system to the tank and to the water supply with a 1/2-inch pipe. There’s a shut-off valve inside the tank that controls the water flow.”

Flush actions can be mechanical, motion sensors, or infrared.

“A lot of times for commercial applications, they use IR with a mechanical override,” Schmidt says. “Generally, they are done with AC or DC power to deliver the power to the flush.”

Viega also offers a remote option where you can place the flush button up to six feet away from the toilet, he explains.

“This is useful in public use ADA applications to provide more options for placing the flush actuator. It makes it more accessible without having to reach over or across the bowl.”


A big part of a successful installation is preplanning.

“Because most piping goes behind the wall, it’s great to have it laid out ahead of time,” advises D’Amato. “Make sure the wall box is located properly so it doesn’t interfere with grab bars behind and to the side of the toilet.”

Another key point is to make sure the sensor is at the correct level to see the user when they are standing and sitting. This can be an issue, particularly with accessibility code requirements mandating seats that have a rise at the back.

One of the biggest installation costs for in-wall systems is generally electrical, D’Amato explains. “Many of the valves have to be individually powered by a transformer.”

Some systems will allow one transformer to power multiple flush valves using a daisy chain approach, however. When planning an in-wall installation, ensure that the wall cavity space is at least six-inches so that it can accommodate a concealed flush valve. Roughing in the piping and carrier is essential.

“It’s critical that you install everything at the correct height for the sensors to work. Where you have accessibility code requirements for back rests on toilet seats, the sensor should be 2-1/2” above the top of the seat cover,” Walker says. And mounting rods need to be properly positioned, otherwise the bowl may feel unstable.

The most important part of pre-planning, advises Schmidt, is to simply pay attention to the installation instructions from the manufacturer. “It’s a relatively easy installation if you pay attention,” he says. “You would be surprised how many installers are not familiar with these installations.”


Flushometers are manufactured in two different technologies – diaphragm and piston. Deciding which is best is based on such factors as the volume of traffic, water conditions (acidity, dirty water, corrosive water, treated) and operating conditions (i.e. water pressure factors).

Diaphragm technology can accommodate the quick recovery needed to immediately flush again, whereas low-traffic situations can benefit from either technology, and certain piston designs can offer additional cleaning and maintenance features.


An essential question is whether to go with vertical or horizontal carriers.

Carol Brown, drainage manager for Watts, notes that 90 per cent of installations are going to need horizontal carriers. “While horizontal flowing systems don’t affect the bowl, they do affect what’s behind the wall,” she says.

Then the decision is whether you need a right-hand or left-hand carrier. “In other words, when the toilet is hung, which way will the waste flow towards the stack?”

If there are multiple banked toilets that flow left (or right), the last in the line would need to be vertical. For larger projects with bathrooms on every floor, Brown says the banked toilet setup can be prefabricated in the shop so the system can be more easily plumbed in and attached behind the wall.


With in-wall carrier systems, it’s essential to establish a maintenance schedule.
“These are electronic systems with moving parts,” Walker says. “People install these and figure they can put them in and walk away. But that’s not the case.”

The frequency of check-ins depends on the water quality. “A good time to do your first check is a year after installation. Then you can set up a maintenance schedule to check the flush valves and solenoids,” he adds.

And Schmidt advises that it is a good practice to program the system to perform a hygienic flush every so many hours, based on the water quality of the building.