WATER People who complain when it rains are not looking at the positive. People who complain when it rains are not looking at the positive – all that water helps barley and hops to grow! It also fills Britain’s reservoirs, streams and springs meaning that brewers have a ready source of the most fundamental ingredient in beer. Beer is composed of up to 95% water and its quality and composition is crucial. Water contains varying amounts of mineral salts depending on the geology of the rocks it percolates through. These salts influence the taste, mouthfeel and the style of beer.