Exhaust adapter, exhaust structure for water heater, and method for installing exhaust adapter

An exhaust structure for water heater connected to a water heater, comprising:

• an exhaust tube which has one end and the other end and is connected to said water heater at said one end;
• an exhaust pipe into which a part of said exhaust tube at the other end thereof is inserted;
• and
• an exhaust adapter which is formed to have an annular shape enclosing a through hole, and is mounted on an outer peripheral surface of said exhaust tube by inserting said exhaust tube into said through hole and is mounted on an inner peripheral surface of said exhaust pipe,
• when said exhaust adapter being fitted on said outer peripheral surface of said exhaust tube, an inner peripheral surface of said exhaust adapter pressing said outer peripheral surface of said exhaust tube, and when said exhaust adapter being fitted on said inner peripheral surface of said exhaust pipe, an outer peripheral surface of said exhaust adapter pressing said inner peripheral surface of said exhaust pipe, wherein
• the exhaust adapter includes an annular member including one end surface and the other end surface facing each other and including said through hole penetrating across said one end surface and the other end surface, and an outer peripheral projection member having an annular shape and projecting from an outer peripheral surface of said annular member outward circumferentially,
• the outer peripheral projection member includes a plurality of projections which are spaced apart from each other on the outer peripheral surface of the annular member,
• the plurality of projections include a first projection and a second projection and the outer peripheral surface of the annular member between the first projection and the second projection extends in an axis direction of the annular member while maintaining an outer diameter of the annular member,
• the annular member is mounted on said exhaust tube in such a way that one end surface of said annular member is positioned closer to the other end of said exhaust tube than the other end surface thereof,
• the outer peripheral projection member is configured to press said inner peripheral surface of said exhaust pipe,
• said exhaust tube is provided with a recess on said outer peripheral surface,
• said exhaust adapter further includes an inner peripheral projection member having an annular shape and projecting from an inner peripheral surface of said annular member inward circumferentially so as to fit in said recess of said exhaust tube,
• said exhaust tube is a flexible tube, and
• a portion of said inner peripheral surface of said annular member other than said inner peripheral projection member extends in an axis direction of said annular member while maintaining an inner diameter of said annular member.