Wall-hung toilets have the great advantage of leaving room beneath the toilet, making the floor a continuum and it’s easy to clean underneath the toilet. Two types exist that will be discussed in the next section.
The first type of toilet is all external, nothing is built in. This means all the parts of the toilet including the tank are visible. This has the advantage that if something malfunctions it can easily be fixed or replaced.
Installation of such a toilet can be difficult if you are replacing a regular toilet. The outlet pipe will be in the floor, and for this model the outlet pipe has to be inside the wall. This could be difficult to change. The next model doesn’t have this problem as much.
The second model has a built in tank. Only the bowl and the buttons are visible. This makes an very elegant and minimalist impression. Just as the model discussed above it is easy to clean underneath it. You don’t have bolt caps underneath your toilet that get dirty like the regular toilet.. It is however more expensive and more difficult to install. The outlet pipe remains in the floor but may have to be moved closer to the wall. The frame where the water tank is in is mounted against the wall. The frame is strong enough to carry the bowl and the person on it. After installation it can be covered with gypsum plates and subsequently covered with tiles. By removing the plastic part with the buttons there is still some access for to most parts of the flushing mechanism, though limited. It requires more work, but can be very much worth it.
Two well-known American manufacturers who produce wall hung toilets with built in tanks are Toto and Kohler. You can buy the bowls for approximately 300 dollar, but you also need the water tank with the frame. As the Toto and Kohler wall hung toilets aren’t standard there is still limited choice in the carrier frame with built in tank of the same brand (you have to buy them separate). A less expensive option is to buy a Geberit toilet carrier frame with water tank and to combine it with a Toto wall hung toilet or one of Kohler. This frame of Geberit is significantly cheaper than the Toto equivalent and has better reviews Geberit Toilet Carrier Frame Dual-Flush Tank. Geberit has decades of experience with in wall systems for toilets. On the Geberit website you can find more information on Geberit in wall systems for toilets.
Do realize you have to buy a flush actuator plate too. As you expect a Toto wall hung toilet will still be more expensive than a standard toilet.