Pressure bathtub / product design

Pressure Bathrub is to use a person's weight.
Weight as coming under pressure to adjust
the amount of water is characteristic.
By using different weight which everybody has, by applying pressure of a person's weight to the bathtub, you can use only as much water as you need. And it can made you use as two times or less of water as usual.
Lack of pressure control and using the sensor to adjust the amount of water.
weight at about 2-3 times as much pressure, who will send the waterflow.Usually the total amount of the bathrub is 300 - 500 liters. Even if people think the avarage weight is a waste of too much water in the bathrub.