I have 2 bathrooms upstairs and just had a dartmouth by toto installed in one of the bathrooms and when we are downstaris and we flush the toilet we hear a loud rushing sound of water going threw the pipes for 1 minute or so we do not hear this when we flish the other toilet by mansfield we never heard this loud rushing sound with our old toilet can there be an leak in the pipes or is it the force of the toto toilet working?