[drover]

I took the header tank hose off from the hose junction as I had fears the plastic bit on the header tank might break.....

I drained mine into a container so I could see how much I got out, supposed to hold 11.5 lts, drained from radiator I got about 4.5lts, about another 6ish out of the engine by the time it started to clear ............. mine was actually just cloudy not muck so it hasn't had town water added at any time......

Once did a service on my Cruiser at work many years ago, used the tank water, a few weeks later I saw my coolant was like mud, I then found out as the tank was low and big winds expected they filled it with town water so it didn't move............ Lots of Crows around that morning.

I had a 20lt drum which I had fitted a tyre valve and a 12mm hose from the tap fitting which you could fill with coolant, keep it at 10psi and it would push the coolant out, used it to refill a Solar HWS, hoped it would work on the by pass hose but the 3mm by pass opening was just too restrictive.