Dirty water from taps! (Worcester Combi-Boiler)

[Olympus]

I have a Worcester 24i RSF combi-boiler that is about 8 years old and feeds four rads in my flat.

Lately, I have been getting dirty water from the taps. It looks and smells like the water in the rads, grey in colour and smells metallic. It clears after a short while. It appears from both the hot and the cold taps in the kitchen and bathroom, whether the heating is on or not.

I have just drained the system and replaced a radiator that was sludged up. I have also injected Fernox cleaner into one of the rads.

I thought the water to the taps came straight from the rising main. Why might it be getting contaminated like this?

 

[Nixt]

Your main heat exchanger may be leaking where it transfers heat to the secondary side (HW). To test watch if the boiler pressure gauge rises late at night (when mains pressure is higher). The 24i RSF has a single bi-thermic heat exhanger which will be more costly than a separate secondary plate type.