Why does it sound different than a gravity toilet?
While there is no way to control the sound of a Flushmate-equipped toilet, there are essentially three factors to consider.
The first factor is the environment in which the toilet is installed. The perceived noise level of a toilet flushed in a relatively small powder room, with ceramic tile flooring, flat bare walls and hard counter tops will be significantly different than that of the same toilet flushed in a large master suite bathroom, with more architectural features to break up the area into smaller sub-sections and softer floor and wall treatments. The noise levels produced by the toilet itself will be essentially the same, but the makeup of the surrounding environment will have a distinct influence on the perceived level of noise.
Secondly, the characteristics of the toilet will have a direct influence on the nature and levels of sound produced during flushing. By design, the majority of water released with each flush is directed to a jet located at the bottom of the toilet bowls water reservoir. The intent of this is to use the force of the water jet to eliminate the waste and water from the bowl and move it into the trap-way of the bowl. There is a unique phenomenon associated with this. If you will observe the jet of a pressure assist toilet during the flush cycle, you will note that there is a distinct change in noise when the water level in the bowl drops below that of the jet. The reason for this is that the water covering the jet absorbs and dampens a significant amount of the noise produced by the water exiting the jet. When the water level drops below the jet, this dampening effect is lost. This factor is a characteristic of the bowls design. During development of a toilet bowel, a careful balance is established between the volume of water passing through the jet to evacuate the bowl, and the volume of water directed to the rim to wash down the sides of the bowl and refill it. Please keep in mind that the volume of water directed to the jet must be sufficient to clear the waste and carry it through the drain system.
The third factor is the pressure assist system itself. The system is designed to operate with the mandated 1.6 gallons of water and produce a flush that clears the bowl of waste and ensures it is carried through the waste system. To accomplish this, the system moves a significant percentage of the allowable water through the jet in a short period of time. Anytime we move a fluid through a rigid passageway noise is generated. Our testing has shown that while the peak noise levels generated by a pressure assist toilet may be slightly greater than with a gravity toilet, the noise level builds up and drops off faster with the pressure assist system. This could be summarized by saying the noise level is slightly greater but of shorter duration.