Water all over dining room floor

[hamjamwitch]

We had all our radiators replaced today (6).
Central heating all working fine this evening after plumbers had left
But I found water in one corner of the dining room. We have lino, so I could see it behind the recycling bin. I then found lots of black, sludgy water under the dining table. Panicked and thought it was a leak from upstairs but then thought it can't be because new radiator water is clean?
Could it be dirty water from the old radiator that was taken off the dining room wall? If they put it down on the floor for a short while, the water might have leaked. Anyway, I just finished mopping it all up. It smells like rust.
How could they not have seen it !

They've chose to ignore it. It will be out of the old radiators.

Thank you for replying. I'm hoping this is what has happened because then I know it's not leaking from anywhere now. I panicked when I found the water all under the table

It does sound like radiator sludge.

As you say, the new ones will be clean as a whistle.