As Rhino says. If you really need to lose it - let it go!
I've been a ground victim of this some years ago.
I live approx 5 miles crow flight slightly left of centre of LGW 26L and had the misfortune to be in the garden when a TransAero A300 came grinding over obviously struggling to gain height on one engine. I estimated that this aircraft was no more than 1500 feet agl. As I looked up I could feel and taste the fuel it was dumping (it was invisible). The aircraft then flew directly over the town of Horsham, still dumping. I was a little concerned (not least for Mrs Speedpig's washing on the line) and called Gatwick Tower to lodge my first and only ever complaint. I was told by the watch manager that the aircraft was in dire emergency and had no choice but to dump asap. I questioned the wisdom of the aircraft being vectored over a large town in that condition and was told that ATC had no control over where the captain decided to go!!! Is this true?
Fortunately, the aircraft landed safely back at LGW.
SP