A support and connection structure suitable to support a tank during a hydrostatic acceptance test and suitable to connect the tank to a feed line of a test fluid, said structure comprising: - a support and housing base for the tank ; - a sealing joint with an axial extension along an axis (G) and a circumferential extension perpendicularly to said axis (G), configured to connect the support and housing base with the tank , a feeding conduit axially passing through the fluidic connection between the feed line and the inside of the tank being obtained in said sealing joint , wherein the support and housing base comprises a clamp formed by at least one pair of jaws configured to pass from a disengaged position to a support position of the sealing joint along said circumferential extension and of the tank along said axis (G), a joint housing seat and a connecting pipe for the connection of the feed line with the feeding conduit also being obtained in the support and housing base , wherein the sealing joint comprises a base engagement element sealingly engageable with the support and housing base , and a connecting nipple , the connecting nipple extending between a first end engageable in the nipple engagement hole , and a second end (52") at least partially externally threaded so it is engageable in a respective threaded hole obtained in the tank , the structure characterized in that the base engagement element comprising a centering portion and a head which surmounts said centering portion in axial succession, wherein i) the centering portion is engageable in the joint housing seat with shape and/or force coupling, ii) the head has a greater circumferential volume than the one of the centering portion , a nipple engagement hole configured to engage the connecting nipple also being obtained in the head. - a support and housing base for the tank ; - a sealing joint with an axial extension along an axis (G) and a circumferential extension perpendicularly to said axis (G), configured to connect the support and housing base with the tank , a feeding conduit axially passing through the fluidic connection between the feed line and the inside of the tank being obtained in said sealing joint , wherein the support and housing base comprises a clamp formed by at least one pair of jaws configured to pass from a disengaged position to a support position of the sealing joint along said circumferential extension and of the tank along said axis (G), a joint housing seat and a connecting pipe for the connection of the feed line with the feeding conduit also being obtained in the support and housing base , wherein the sealing joint comprises a base engagement element sealingly engageable with the support and housing base , and a connecting nipple , the connecting nipple extending between a first end engageable in the nipple engagement hole , and a second end (52") at least partially externally threaded so it is engageable in a respective threaded hole obtained in the tank , the structure characterized in that the base engagement element comprising a centering portion and a head which surmounts said centering portion in axial succession, wherein i) the centering portion is engageable in the joint housing seat with shape and/or force coupling, ii) the head has a greater circumferential volume than the one of the centering portion , a nipple engagement hole configured to engage the connecting nipple also being obtained in the head. i) the centering portion is engageable in the joint housing seat with shape and/or force coupling, ii) the head has a greater circumferential volume than the one of the centering portion , a nipple engagement hole configured to engage the connecting nipple also being obtained in the head. <EOS>