We have a new Drake II Toto I installed two weeks ago. Looks great and flushes great, but one minor problem. After about one week, there is a short high-pitched squeak / honk noise when you flush - right as it starts to refill the tank and another at the end of the refill cycle. The water feed valve at the wall is all the way open. Is there an adjustment I can make, or is this a faulty valve? Thanks!