The black death has nothing to do with dirt in the water!
I have had it once and it happend when i was not looking when i answered a phone call.
To make it worse, it was a mega,mega expensive patterned wool carpet and a well to do customer.
Luckily the customer was in the garden at the time, so i covered the carpet with sheets before she came in and i frantically tried to sort it out every time she disappeared.
Thankfully i just about got away with it, but a 2 hrs job took 10hrs
I always keep a empty bucket within running distance now.