A hot water appliance comprising: - a water tank comprising a water tank wall; - a heating element included in the water tank; - a vacuum vessel enclosing a vacuum space, the water tank being wholly included in the vacuum space, the whole water tank wall being bounded by vacuum, the vacuum vessel comprising a vacuum vessel wall consisting of a number of vacuum vessel wall parts gastightly connected with each other by welding or soldering; - at least one functional pipe (100, 200, 300, 400 and/or 500) extending through the water tank wall and being gastightly connected with the water tank wall at the location of a water tank wall connection, and the functional pipe (100, 200, 300, 400 and/or 500) extending also through the vacuum vessel wall and being gastightly connected with the vacuum vessel wall at the location of a vacuum vessel wall connection; characterized in that the at least one functional pipe (100, 200, 300, 400, 500) comprises a first pipe part (102, 202, 302, 402, 502), a first bend (104, 204, 304, 404, 504) which connects the first pipe part (102, 202, 302, 402, 502) with a second pipe part (106, 206, 306, 406, 506), a second bend (108, 208, 308, 408, 508) which connects the second pipe part (106, 206, 306, 406, 506) with a third pipe part (110, 210, 310, 410, 510); wherein the first pipe part (102, 202, 302, 402, 502) extends through an upper side of the vacuum vessel; wherein the third pipe part (110, 210, 310, 410, 510) extends through a bottom side of the water tank; wherein the first pipe part (102, 202, 302, 402, 502) extends substantially vertically between the water tank wall and the vacuum vessel wall. - a water tank comprising a water tank wall; - a heating element included in the water tank; - a vacuum vessel enclosing a vacuum space, the water tank being wholly included in the vacuum space, the whole water tank wall being bounded by vacuum, the vacuum vessel comprising a vacuum vessel wall consisting of a number of vacuum vessel wall parts gastightly connected with each other by welding or soldering; - at least one functional pipe (100, 200, 300, 400 and/or 500) extending through the water tank wall and being gastightly connected with the water tank wall at the location of a water tank wall connection, and the functional pipe (100, 200, 300, 400 and/or 500) extending also through the vacuum vessel wall and being gastightly connected with the vacuum vessel wall at the location of a vacuum vessel wall connection; characterized in that the at least one functional pipe (100, 200, 300, 400, 500) comprises a first pipe part (102, 202, 302, 402, 502), a first bend (104, 204, 304, 404, 504) which connects the first pipe part (102, 202, 302, 402, 502) with a second pipe part (106, 206, 306, 406, 506), a second bend (108, 208, 308, 408, 508) which connects the second pipe part (106, 206, 306, 406, 506) with a third pipe part (110, 210, 310, 410, 510); wherein the first pipe part (102, 202, 302, 402, 502) extends through an upper side of the vacuum vessel; wherein the third pipe part (110, 210, 310, 410, 510) extends through a bottom side of the water tank; wherein the first pipe part (102, 202, 302, 402, 502) extends substantially vertically between the water tank wall and the vacuum vessel wall. the at least one functional pipe (100, 200, 300, 400, 500) comprises a first pipe part (102, 202, 302, 402, 502), a first bend (104, 204, 304, 404, 504) which connects the first pipe part (102, 202, 302, 402, 502) with a second pipe part (106, 206, 306, 406, 506), a second bend (108, 208, 308, 408, 508) which connects the second pipe part (106, 206, 306, 406, 506) with a third pipe part (110, 210, 310, 410, 510); wherein the first pipe part (102, 202, 302, 402, 502) extends through an upper side of the vacuum vessel; wherein the third pipe part (110, 210, 310, 410, 510) extends through a bottom side of the water tank; wherein the first pipe part (102, 202, 302, 402, 502) extends substantially vertically between the water tank wall and the vacuum vessel wall.