Scale trap and water heater

Scale trap 5, a casing 5a that inlet and outlet of water is formed at both ends, a representative length than scale particles larger opening 10 is formed with a plurality, a scale deposition body 8 filled in the casing 5a provided, the casing 5a, the cavity region 9 is formed at an end of the side as the inlet of at least water, a central portion of the end portion bottom surface of the inlet side of the scale trap inlet pipe 11 is the casing 5a, bottom surface is connected in a direction perpendicular to the scale trap inlet pipe 11, the cavity region 9 and scale adhesion member 8 is arranged on a straight line, in which water flows in a certain direction.