Rusty water is not a good sign it indicates air infiltration.
Probable cause is that the vent and feed to the system have the pump in between them causing the water to pump over at the vent thus aerating the water. A leaky valve or pump dragging air in on a part of the system where the pump is 'pulling' can cause it as well.
My recommendation now is to fit a de-aerator and get a powerflush, done correctly this would remove air from your system in the way you require.
Rust can permanently block up waterways in a radiator so it may be that you also need to invest in a few rads sooner or later.
Black water is a better sign. Although it indicates deterioration of your system its a slower process and can be remedied best with a powerflush. Ordinary flushing with additives is also effective but leaves more crud in your system and wont clear blockages as well as powerflushing.
Probable cause is that the vent and feed to the system have the pump in between them causing the water to pump over at the vent thus aerating the water. A leaky valve or pump dragging air in on a part of the system where the pump is 'pulling' can cause it as well.
My recommendation now is to fit a de-aerator and get a powerflush, done correctly this would remove air from your system in the way you require.
Rust can permanently block up waterways in a radiator so it may be that you also need to invest in a few rads sooner or later.
Black water is a better sign. Although it indicates deterioration of your system its a slower process and can be remedied best with a powerflush. Ordinary flushing with additives is also effective but leaves more crud in your system and wont clear blockages as well as powerflushing.