@ Amit......... excess water intake leads to extra burden on kidney and heart because ingesting more water than you need can increase your total blood volume which in turn burdens your heart and blood vessels.
Your kidneys must work overtime to filter excess water out of your blood circulatory system to maintain the mineral balance in your body.
As your blood circulatory system becomes diluted with excess water, the concentration of electrolytes in your blood will drop relative to the concentration of electrolytes in your cells. In an effort to maintain an equal balance of electrolytes between your blood and your cells, water will seep into your cells from your blood, causing your cells to swell.If this swelling occurs in your brain, the bones that make up your skull hardly budge hence it may lead to mild headache or sometimes even impaired breathing .For an average person it is little difficult to even notice all these symptoms.
So keep in mind that moderation is the key for everything.