Prophetic Sunnahs are firmly established,
including moderation in the use of water.
It is narrated on the authority of Anas (may Allah be pleased with him) that he said:
"The Prophet (peace and blessings of Allah be upon him) used to perform ritual bath (ghusl) with a sa' up to five mudds of water,
and he would perform ablution (wudu) with a single mudd."