Sayyidi wa sanadi Mufti Mohammad Taqi Usmani (Allah preserve him) said,

‘We must be careful while performinf wudhu.

Wasting large amounts of water is sinful.

Our master Prophet (Allah bless him and grant him peace) said in regards to wudhu, 

‘Don’t waste water even if you are performing it at a riverbank.’

The Sunna amount of water to use in wudhu is approximately  775 ml. (That is less than a liter.)’

Waaz, May 2014

(Mudd:The picture above shows a container of this capacity)