I had on a number of occasions seen Imamdoing wudhu. In between each of the actions of wudhu, Imam would close the tap for fear of wasting water. Only when it was necessary would he open the tap.
Many of us do not take care not to waste water. Whereas when Imam wanted to do wudhu, he took a lot of care to make sure water was not wasted.
(A memoirs by Agha Mahmood Bouroujerdi-Imam's son in law)