your hot water is coming from a storage tank check this tank to see any contamination make sure tank as lid and sealed correctly if all loks ok use what hot water you have and let cylinder go cold and flush through water through hot tap for 10mins should clear any contamination from tank
the bits probablly are not dangerous but maybe plastic pipe shavings from works carried out on water mains outside and once water re-enstated the first property to use the supply has the pleasure of getting this debre,such is life
Of course they could be from outer space.................:-)
tony
March 2008