try dave clarke a ring 01772612118 . the pipe at the top is ok as it is ! dont put the vent pipes in to far and drain the tank from time to time they do fill up ! theres screw at the bottom !
I route the radiator overflow to the large vent. Use a hot nail to poke a vent hole on top after. I've got the water pump weep hole going there too with 1/8 inch tubing.