the pressure in the system is one bar.. 16 psi.. max and you can use an old bicycle tyre inner tube section complete with its tyre valve to pump up the system to 1 bar... after that pressure the vent cap will vent..
thats an expensive old tyre valve you show...
one can just unhook the jiggle pipe return pipe and add the tyre piece complete with valve... for pennies... some bits of hose to adapt the different diameters and jubilee clips.
it really doesnt take much to contain 16 psi... and you can pump it up with a tyre pump.. if you pump too much... the vent cap vents... so you get to check two things at once... that the vent cap works and the system holds pressure. it will take a long time for it loose pressure if you have no leaks.... up to two hours to go from 15 psi to 3 psi... if it happens in five minutes.. you have a leak.
pop down to your local bicycle repair shop and ask them if they have an old inner tube
Last edited by Incony; 20-04-2017 at 20:34.