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 (V), the water tank being wholly included in the vacuum space (V), 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 comprises a first pipe part , a first bend which connects the first pipe part with a second pipe part , a second bend which connects the second pipe part with a third pipe part ; wherein the first pipe part extends through an upper side of the vacuum vessel ; wherein the third pipe part extends through a bottom side of the water tank ; wherein the first pipe part 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 (V), the water tank being wholly included in the vacuum space (V), 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 comprises a first pipe part , a first bend which connects the first pipe part with a second pipe part , a second bend which connects the second pipe part with a third pipe part ; wherein the first pipe part extends through an upper side of the vacuum vessel ; wherein the third pipe part extends through a bottom side of the water tank ; wherein the first pipe part extends substantially vertically between the water tank wall and the vacuum vessel wall . the at least one functional pipe comprises a first pipe part , a first bend which connects the first pipe part with a second pipe part , a second bend which connects the second pipe part with a third pipe part ; wherein the first pipe part extends through an upper side of the vacuum vessel ; wherein the third pipe part extends through a bottom side of the water tank ; wherein the first pipe part extends substantially vertically between the water tank wall and the vacuum vessel wall . <EOS>