Connection system of piping for distribution systems of pressurised or depressurised fluids, wherein the connection system comprises a piping, said piping comprises at least a section of rigid bar, which is quadrangular in shape, which extends longitudinally and, internally, has a hole for the passage of the fluid, and, on its outer surface, at its corners, four, dovetailed, outwardly open grooves are made radially and delimited laterally by two rims, wherein the connection system further comprises: - a connection joint comprising an insertion portion sealingly insertable in the hole and a retention portion projecting from the piping when the joint is inserted therein, the retention portion having outwardly at least one circular retention slot; - retention means suitable to longitudinally retain the connection joint to the piping, said retention means comprising: i) a retention element suitable to engage the retention portion by inserting itself in said retention slot; and ii) clamping means suitable to act with the rims of two consecutive grooves and with the retention element, and suitable to exert a clamping force to the rims of the two consecutive grooves to block the retention element to the piping, the clamping means comprising an upper clamp and a lower clamp respectively having a first tooth and a second tooth suitable for being placed inside the respective groove engaging the respective rim and wherein the upper clamp and/or the lower clamp has a channelling (410, 420); the connection system is characterised by the fact that the retention element comprises: - at least one bracket having an arched retention blade suitable to engage the retention slot, and two clamping branches, which extend laterally to and perpendicularly to the sides of the retention blade and are suitable to engage with the clamping means, which is housing the clamping branch, to block the retention element and thus the joint to the piping wherein the clamping branches comprise at least one blocking portion, which extends from the respective clamping branch, and by engaging with the clamping means prevents the longitudinal translation of the bracket. - a connection joint comprising an insertion portion sealingly insertable in the hole and a retention portion projecting from the piping when the joint is inserted therein, the retention portion having outwardly at least one circular retention slot; - retention means suitable to longitudinally retain the connection joint to the piping, said retention means comprising: i) a retention element suitable to engage the retention portion by inserting itself in said retention slot; and ii) clamping means suitable to act with the rims of two consecutive grooves and with the retention element, and suitable to exert a clamping force to the rims of the two consecutive grooves to block the retention element to the piping, the clamping means comprising an upper clamp and a lower clamp respectively having a first tooth and a second tooth suitable for being placed inside the respective groove engaging the respective rim and wherein the upper clamp and/or the lower clamp has a channelling (410, 420); i) a retention element suitable to engage the retention portion by inserting itself in said retention slot; and ii) clamping means suitable to act with the rims of two consecutive grooves and with the retention element, and suitable to exert a clamping force to the rims of the two consecutive grooves to block the retention element to the piping, the clamping means comprising an upper clamp and a lower clamp respectively having a first tooth and a second tooth suitable for being placed inside the respective groove engaging the respective rim and wherein the upper clamp and/or the lower clamp has a channelling (410, 420); - at least one bracket having an arched retention blade suitable to engage the retention slot, and two clamping branches, which extend laterally to and perpendicularly to the sides of the retention blade and are suitable to engage with the clamping means, which is housing the clamping branch, to block the retention element and thus the joint to the piping wherein the clamping branches comprise at least one blocking portion, which extends from the respective clamping branch, and by engaging with the clamping means prevents the longitudinal translation of the bracket.