Abstract: A connection assembly for connecting flexible tubes such as flexible tubes of a solar heat exchanger to a header pipe. The connection assembly includes a tubular spigot member which co-acts at one end with a sleeve to compress the tube and maintain the tube in sealing engagement with the spigot member. The opposite end of the spigot member is engaged with the header pipe by means of a hollow flexible plug which is located in an aperture in the header pipe and which expands radially outwardly on engagement with the spigot member to prevent withdrawal of the spigot member and ensure efficient sealing therearound.