Aqua-Rex will get rid of Calcium scale but will have little or no effect on Silica scale. Silica scale is only an issue in a few areas of the country where Silica rich water is drawn from wells. Silica scale won’t react to acids such as Vinegar or Muriatic and can only be removed by using abrasives. Sometimes you will find all the scale disappears and then a thin layer recurs and this is likely to be Silica. Scale around the grout line of a swimming pool comes from behind the tile and is mostly Silica so Aqua-Rex won’t get rid of it.