Mark has posted the vac pipe layout in the Maintainance Guide section (here)
http://www.omegaowners.com/forum/YaBB.pl?num=1152565204Remember that the system works on vacuum, ie "suck". The pipe from the servo line connects to the vac. reservoir via the in-built non-return valve or your fish tank one, note that the flow is from vac tank to servo pipe.
The vac tank output connects to the T piece, one arm of which connects to the front multiram valve and the other to the rear multiram valve.
When an engine is operating under load it generates very little manifold vacuum so any vacuum operated device would struggle to work when going up hill etc ( ever seen an older car with vacuum wipers? they stopped working when going up hill !). The vacuum tank is there to store the vacuum and get around this problem, the non-return valve allows the engine to suck air out of the reservoir when under light load but shuts if the manifold pressure is higher that that inside the reservoir when accelerating or climbing etc. HTH