The North East zone of the home is the most important region according to Vastu. If North East is made good, rest all zones come in alignment. Even if the other zones are not so supportive and North East is auspicious, then the residents of that home can survive without many difficulties.
According to Vastu, North East zone is the zone of Spiritual Enlightenment and the zone of clarity and awareness. Imagine if you are highly capable, you have all the resources in hand to taking up any task or venture but you lack clarity or wisdom, Whatever effort that is put in wrong direction or wrong way becomes useless.
North East being the zone of water element, it is highly auspicious to place water elements here but there one catch on this. North east should also be the lowest height zone of the entire house. Hence you should place underground water tank here which will satisfy both these conditions.
Placing underground water tank in North east will bring opportunities, prosperity, wealth, clarity in mind and wisdom.