Dirty water from taps! (Worcester Combi-Boiler)

I have a Worcester 24i combi-boiler. It’s about 8 years old and feeds 4 rads. It’s a sealed system of course, so there are no storage tanks.

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.

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 and will soon drain that off and inject Fernox inhibitor.

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

Thanks guys!

Leaking heat exchanger?

If the boiler uses a shell and tube heat exchanger design, hydronic water (heated in the Shell) is getting into the hot water supply (heated in the tube which is in the Shell).

I am not familiar with your particular boiler, but this is what I would suspect.

Yes.

If you have an indirect water heater, this could be the source of contamination.

It is particulatly bad if your boiler runs propylene glycol or some other anti-freezing chemical in its lines.

Yes, Glycol will cause kidney failure.