The system now appears to be working OK, but I have some questions:
> First, have I omitted anything or is the system good to go?
> There was a certain amount (but not much) of black sludge, and the
> Collins book suggests using an anti-corrosion aid in the water - how
> can I get that into a pressurised system? Is it necessary?
It is absolutely essential to install corrosion inhibitor. On a pressurised system, there are a number of solutions to getting the stuff into the system. It is possible to get it concentrated into a syringe that you insert into the bleed valve on a suitable radiator.
My preferred technique is to add an additive point when the system is drained down. This consists of a T piece with a short length of pipe sticking vertically upwards terminated by an isolation valve and another short length of pipe. You can then stick a funnel in and pour what you like before refilling. Just remember to turn the valve off before starting the filling loop up! Using this method you can use standard inhibitor which is much cheaper than proprietary injection systems.
Further, I guess this will be at (or level with) the lowest point in
>the system. I can't find it anywhere on the lower floor, though -
>any suggestions as to where I could find it?
There might not be one. Install one yourself if you get the chance.
Christian.